diff --git a/.editorconfig b/.editorconfig
index de41f1de01..885c40bd93 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -42,9 +42,9 @@ dotnet_style_qualification_for_method = false:suggestion
 dotnet_style_qualification_for_event = false:suggestion
 
 # Types: use keywords instead of BCL types, and permit var only when the type is clear
-csharp_style_var_for_built_in_types = false:suggestion
-csharp_style_var_when_type_is_apparent = false:none
-csharp_style_var_elsewhere = false:suggestion
+csharp_style_var_for_built_in_types = true:suggestion
+csharp_style_var_when_type_is_apparent = true:none
+csharp_style_var_elsewhere = true:suggestion
 dotnet_style_predefined_type_for_locals_parameters_members = true:suggestion
 dotnet_style_predefined_type_for_member_access = true:suggestion
 
diff --git a/src/ReactiveUI.Fody.Analyzer.Test/Helpers/CodeFixVerifier.Helper.cs b/src/ReactiveUI.Fody.Analyzer.Test/Helpers/CodeFixVerifier.Helper.cs
index 04cf86496a..d60e69b77f 100644
--- a/src/ReactiveUI.Fody.Analyzer.Test/Helpers/CodeFixVerifier.Helper.cs
+++ b/src/ReactiveUI.Fody.Analyzer.Test/Helpers/CodeFixVerifier.Helper.cs
@@ -48,8 +48,8 @@ private static IEnumerable<Diagnostic> GetNewDiagnostics(IEnumerable<Diagnostic>
             var oldArray = diagnostics.OrderBy(d => d.Location.SourceSpan.Start).ToArray();
             var newArray = newDiagnostics.OrderBy(d => d.Location.SourceSpan.Start).ToArray();
 
-            int oldIndex = 0;
-            int newIndex = 0;
+            var oldIndex = 0;
+            var newIndex = 0;
 
             while (newIndex < newArray.Length)
             {
diff --git a/src/ReactiveUI.Fody.Analyzer.Test/Helpers/DiagnosticResult.cs b/src/ReactiveUI.Fody.Analyzer.Test/Helpers/DiagnosticResult.cs
index 538166b3dc..018c7c128d 100644
--- a/src/ReactiveUI.Fody.Analyzer.Test/Helpers/DiagnosticResult.cs
+++ b/src/ReactiveUI.Fody.Analyzer.Test/Helpers/DiagnosticResult.cs
@@ -91,7 +91,7 @@ public bool Equals(DiagnosticResult other) =>
         /// <inheritdoc/>
         public override int GetHashCode()
         {
-            int hashCode = 1054991603;
+            var hashCode = 1054991603;
             hashCode = (hashCode * -1521134295) + EqualityComparer<IList<DiagnosticResultLocation>>.Default.GetHashCode(_locations);
             hashCode = (hashCode * -1521134295) + EqualityComparer<IList<DiagnosticResultLocation>>.Default.GetHashCode(Locations);
             hashCode = (hashCode * -1521134295) + Severity.GetHashCode();
diff --git a/src/ReactiveUI.Fody.Analyzer.Test/Helpers/DiagnosticVerifier.Helper.cs b/src/ReactiveUI.Fody.Analyzer.Test/Helpers/DiagnosticVerifier.Helper.cs
index 5af168e04c..de4cb0f259 100644
--- a/src/ReactiveUI.Fody.Analyzer.Test/Helpers/DiagnosticVerifier.Helper.cs
+++ b/src/ReactiveUI.Fody.Analyzer.Test/Helpers/DiagnosticVerifier.Helper.cs
@@ -148,8 +148,8 @@ private static Document[] GetDocuments(string[] sources, string language)
         /// <returns>A Project created out of the Documents created from the source strings.</returns>
         private static Project? CreateProject(string[] sources, string language = LanguageNames.CSharp)
         {
-            string fileNamePrefix = DefaultFilePathPrefix;
-            string fileExt = language == LanguageNames.CSharp ? CSharpDefaultFileExt : VisualBasicDefaultExt;
+            var fileNamePrefix = DefaultFilePathPrefix;
+            var fileExt = language == LanguageNames.CSharp ? CSharpDefaultFileExt : VisualBasicDefaultExt;
 
             var projectId = ProjectId.CreateNewId(debugName: TestProjectName);
 
@@ -163,7 +163,7 @@ private static Document[] GetDocuments(string[] sources, string language)
                 .AddMetadataReference(projectId, ReactiveUi)
                 .AddMetadataReference(projectId, ReactiveUiHelper);
 
-            int count = 0;
+            var count = 0;
             foreach (var source in sources)
             {
                 var newFileName = fileNamePrefix + count + "." + fileExt;
diff --git a/src/ReactiveUI.Fody.Analyzer.Test/Verifiers/DiagnosticVerifier.cs b/src/ReactiveUI.Fody.Analyzer.Test/Verifiers/DiagnosticVerifier.cs
index 878bf23597..f4464ca9ba 100644
--- a/src/ReactiveUI.Fody.Analyzer.Test/Verifiers/DiagnosticVerifier.cs
+++ b/src/ReactiveUI.Fody.Analyzer.Test/Verifiers/DiagnosticVerifier.cs
@@ -74,20 +74,20 @@ public abstract partial class DiagnosticVerifier
         /// <param name="expectedResults">Diagnostic Results that should have appeared in the code.</param>
         private static void VerifyDiagnosticResults(IEnumerable<Diagnostic> actualResults, DiagnosticAnalyzer analyzer, params DiagnosticResult[] expectedResults)
         {
-            int expectedCount = expectedResults.Length;
+            var expectedCount = expectedResults.Length;
             var actualCountList = actualResults.ToList();
-            int actualCount = actualCountList.Count;
+            var actualCount = actualCountList.Count;
 
             if (expectedCount != actualCount)
             {
-                string diagnosticsOutput = actualCountList.Any() ? FormatDiagnostics(analyzer, actualCountList.ToArray()) : "    NONE.";
+                var diagnosticsOutput = actualCountList.Any() ? FormatDiagnostics(analyzer, actualCountList.ToArray()) : "    NONE.";
 
                 Assert.True(
                     false,
                     $"Mismatch between number of diagnostics returned, expected \"{expectedCount}\" actual \"{actualCount}\"\r\n\r\nDiagnostics:\r\n{diagnosticsOutput}\r\n");
             }
 
-            for (int i = 0; i < expectedResults.Length; i++)
+            for (var i = 0; i < expectedResults.Length; i++)
             {
                 var actual = actualCountList[i];
                 var expected = expectedResults[i];
@@ -113,7 +113,7 @@ private static void VerifyDiagnosticResults(IEnumerable<Diagnostic> actualResult
                                       $"Expected {expected.Locations.Count - 1} additional locations but got {additionalLocations.Length} for Diagnostic:\r\n    {FormatDiagnostics(analyzer, actual)}\r\n");
                     }
 
-                    for (int j = 0; j < additionalLocations.Length; ++j)
+                    for (var j = 0; j < additionalLocations.Length; ++j)
                     {
                         VerifyDiagnosticLocation(analyzer, actual, additionalLocations[j], expected.Locations[j + 1]);
                     }
@@ -192,7 +192,7 @@ private static void VerifyDiagnosticLocation(DiagnosticAnalyzer analyzer, Diagno
         private static string FormatDiagnostics(DiagnosticAnalyzer analyzer, params Diagnostic[] diagnostics)
         {
             var builder = new StringBuilder();
-            for (int i = 0; i < diagnostics.Length; ++i)
+            for (var i = 0; i < diagnostics.Length; ++i)
             {
                 builder.AppendLine("// " + diagnostics[i].ToString());
 
@@ -214,7 +214,7 @@ private static string FormatDiagnostics(DiagnosticAnalyzer analyzer, params Diag
                                 location.IsInSource,
                                 $"Test base does not currently handle diagnostics in metadata locations. Diagnostic in metadata: {diagnostics[i]}\r\n");
 
-                            string resultMethodName = diagnostics[i].Location.SourceTree!.FilePath.EndsWith(".cs", StringComparison.Ordinal) ? "GetCSharpResultAt" : "GetBasicResultAt";
+                            var resultMethodName = diagnostics[i].Location.SourceTree!.FilePath.EndsWith(".cs", StringComparison.Ordinal) ? "GetCSharpResultAt" : "GetBasicResultAt";
                             var linePosition = diagnostics[i].Location.GetLineSpan().StartLinePosition;
 
                             builder.Append($"{resultMethodName}({linePosition.Line + 1}, {linePosition.Character + 1}, {analyzerType.Name}.{rule.Id})");
diff --git a/src/ReactiveUI.Fody.Analyzer/ReactiveObjectAnalyzer.cs b/src/ReactiveUI.Fody.Analyzer/ReactiveObjectAnalyzer.cs
index 51da244307..ce7fe17f2d 100644
--- a/src/ReactiveUI.Fody.Analyzer/ReactiveObjectAnalyzer.cs
+++ b/src/ReactiveUI.Fody.Analyzer/ReactiveObjectAnalyzer.cs
@@ -116,8 +116,8 @@ private static bool HasBackingField(PropertyDeclarationSyntax property)
                 return setter?.ExpressionBody is not null && getter?.ExpressionBody is not null;
             }
 
-            bool setterHasBodyStatements = setter.Body.Statements.Any();
-            bool getterHasBodyStatements = getter.Body.Statements.Any();
+            var setterHasBodyStatements = setter.Body.Statements.Any();
+            var getterHasBodyStatements = getter.Body.Statements.Any();
 
             return setterHasBodyStatements && getterHasBodyStatements;
         }
diff --git a/src/ReactiveUI.Fody.Tests/ApiApprovalBase.cs b/src/ReactiveUI.Fody.Tests/ApiApprovalBase.cs
index 20cc3af022..b1e260247e 100644
--- a/src/ReactiveUI.Fody.Tests/ApiApprovalBase.cs
+++ b/src/ReactiveUI.Fody.Tests/ApiApprovalBase.cs
@@ -45,7 +45,7 @@ protected static void CheckApproval(Assembly assembly, [CallerMemberName]string?
                 var approvedFileName = Path.Combine(sourceDirectory, $"ApiApprovalTests.{memberName}.{targetFrameworkName}.approved.txt");
                 var receivedFileName = Path.Combine(sourceDirectory, $"ApiApprovalTests.{memberName}.{targetFrameworkName}.received.txt");
 
-                string approvedPublicApi = string.Empty;
+                var approvedPublicApi = string.Empty;
 
                 if (File.Exists(approvedFileName))
                 {
diff --git a/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net472.approved.txt b/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net472.approved.txt
index 66195a7794..966c135fce 100644
--- a/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net472.approved.txt
+++ b/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net472.approved.txt
@@ -221,7 +221,7 @@ namespace ReactiveUI
     }
     public interface IObservedChange<out TSender, out TValue>
     {
-        System.Linq.Expressions.Expression Expression { get; }
+        System.Linq.Expressions.Expression? Expression { get; }
         TSender Sender { get; }
         TValue Value { get; }
     }
@@ -317,7 +317,7 @@ namespace ReactiveUI
     }
     public interface ISetMethodBindingConverter : Splat.IEnableLogger
     {
-        int GetAffinityForObjects(System.Type fromType, System.Type toType);
+        int GetAffinityForObjects(System.Type? fromType, System.Type? toType);
         object? PerformSet(object? toTarget, object? newValue, object?[]? arguments);
     }
     public interface ISuspensionDriver
@@ -447,8 +447,8 @@ namespace ReactiveUI
     }
     public class ObservedChange<TSender, TValue> : ReactiveUI.IObservedChange<TSender, TValue>
     {
-        public ObservedChange(TSender sender, System.Linq.Expressions.Expression expression, TValue value) { }
-        public System.Linq.Expressions.Expression Expression { get; }
+        public ObservedChange(TSender sender, System.Linq.Expressions.Expression? expression, TValue value) { }
+        public System.Linq.Expressions.Expression? Expression { get; }
         public TSender Sender { get; }
         public TValue Value { get; }
     }
@@ -600,10 +600,10 @@ namespace ReactiveUI
     }
     public static class ReactiveNotifyPropertyChangedMixin
     {
-        public static System.IObservable<ReactiveUI.IObservedChange<TSender, TValue>> ObservableForProperty<TSender, TValue>(this TSender item, System.Linq.Expressions.Expression<System.Func<TSender, TValue>> property, bool beforeChange = false, bool skipInitial = true) { }
-        public static System.IObservable<TRet> ObservableForProperty<TSender, TValue, TRet>(this TSender item, System.Linq.Expressions.Expression<System.Func<TSender, TValue>> property, System.Func<TValue, TRet> selector, bool beforeChange = false)
+        public static System.IObservable<ReactiveUI.IObservedChange<TSender, TValue?>> ObservableForProperty<TSender, TValue>(this TSender? item, System.Linq.Expressions.Expression<System.Func<TSender, TValue?>> property, bool beforeChange = false, bool skipInitial = true) { }
+        public static System.IObservable<TRet> ObservableForProperty<TSender, TValue, TRet>(this TSender? item, System.Linq.Expressions.Expression<System.Func<TSender, TValue?>> property, System.Func<TValue?, TRet> selector, bool beforeChange = false)
             where TSender :  class { }
-        public static System.IObservable<ReactiveUI.IObservedChange<TSender, TValue>> SubscribeToExpressionChain<TSender, TValue>(this TSender source, System.Linq.Expressions.Expression expression, bool beforeChange = false, bool skipInitial = true, bool suppressWarnings = false) { }
+        public static System.IObservable<ReactiveUI.IObservedChange<TSender, TValue>> SubscribeToExpressionChain<TSender, TValue>(this TSender? source, System.Linq.Expressions.Expression? expression, bool beforeChange = false, bool skipInitial = true, bool suppressWarnings = false) { }
     }
     [System.Runtime.Serialization.DataContract]
     public class ReactiveObject : ReactiveUI.IHandleObservableErrors, ReactiveUI.IReactiveNotifyPropertyChanged<ReactiveUI.IReactiveObject>, ReactiveUI.IReactiveObject, Splat.IEnableLogger, System.ComponentModel.INotifyPropertyChanged, System.ComponentModel.INotifyPropertyChanging
@@ -659,15 +659,15 @@ namespace ReactiveUI
     }
     public static class Reflection
     {
-        public static string ExpressionToPropertyNames(System.Linq.Expressions.Expression expression) { }
+        public static string ExpressionToPropertyNames(System.Linq.Expressions.Expression? expression) { }
         public static System.Type GetEventArgsTypeForEvent(System.Type type, string eventName) { }
-        public static System.Func<object, object?[]?, object?>? GetValueFetcherForProperty(System.Reflection.MemberInfo? member) { }
-        public static System.Func<object, object?[]?, object?> GetValueFetcherOrThrow(System.Reflection.MemberInfo? member) { }
-        public static System.Action<object, object?, object?[]?> GetValueSetterForProperty(System.Reflection.MemberInfo? member) { }
-        public static System.Action<object, object?, object?[]?>? GetValueSetterOrThrow(System.Reflection.MemberInfo? member) { }
+        public static System.Func<object?, object?[]?, object?>? GetValueFetcherForProperty(System.Reflection.MemberInfo? member) { }
+        public static System.Func<object?, object?[]?, object?> GetValueFetcherOrThrow(System.Reflection.MemberInfo? member) { }
+        public static System.Action<object?, object?, object?[]?> GetValueSetterForProperty(System.Reflection.MemberInfo? member) { }
+        public static System.Action<object?, object?, object?[]?>? GetValueSetterOrThrow(System.Reflection.MemberInfo? member) { }
         public static bool IsStatic(this System.Reflection.PropertyInfo item) { }
         public static System.Type? ReallyFindType(string? type, bool throwOnFailure) { }
-        public static System.Linq.Expressions.Expression Rewrite(System.Linq.Expressions.Expression expression) { }
+        public static System.Linq.Expressions.Expression Rewrite(System.Linq.Expressions.Expression? expression) { }
         public static void ThrowIfMethodsNotOverloaded(string callingTypeName, object targetObject, params string[] methodsToCheck) { }
         public static bool TryGetAllValuesForPropertyChain(out ReactiveUI.IObservedChange<, >[] changeValues, object? current, System.Collections.Generic.IEnumerable<System.Linq.Expressions.Expression> expressionChain) { }
         public static bool TryGetValueForPropertyChain<TValue>(out TValue changeValue, object? current, System.Collections.Generic.IEnumerable<System.Linq.Expressions.Expression> expressionChain) { }
@@ -826,97 +826,97 @@ namespace ReactiveUI
     }
     public static class WhenAnyMixin
     {
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Func<ReactiveUI.IObservedChange<TSender, T1>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, ReactiveUI.IObservedChange<TSender, T8>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, ReactiveUI.IObservedChange<TSender, T8>, ReactiveUI.IObservedChange<TSender, T9>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, ReactiveUI.IObservedChange<TSender, T8>, ReactiveUI.IObservedChange<TSender, T9>, ReactiveUI.IObservedChange<TSender, T10>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11>> property11, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, ReactiveUI.IObservedChange<TSender, T8>, ReactiveUI.IObservedChange<TSender, T9>, ReactiveUI.IObservedChange<TSender, T10>, ReactiveUI.IObservedChange<TSender, T11>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11>> property11, System.Linq.Expressions.Expression<System.Func<TSender, T12>> property12, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, ReactiveUI.IObservedChange<TSender, T8>, ReactiveUI.IObservedChange<TSender, T9>, ReactiveUI.IObservedChange<TSender, T10>, ReactiveUI.IObservedChange<TSender, T11>, ReactiveUI.IObservedChange<TSender, T12>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Func<ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Linq.Expressions.Expression property8, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Linq.Expressions.Expression property8, System.Linq.Expressions.Expression property9, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Linq.Expressions.Expression property8, System.Linq.Expressions.Expression property9, System.Linq.Expressions.Expression property10, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Linq.Expressions.Expression property8, System.Linq.Expressions.Expression property9, System.Linq.Expressions.Expression property10, System.Linq.Expressions.Expression property11, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Linq.Expressions.Expression property8, System.Linq.Expressions.Expression property9, System.Linq.Expressions.Expression property10, System.Linq.Expressions.Expression property11, System.Linq.Expressions.Expression property12, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, TRet>> property1) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Func<T1, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2>> WhenAnyValue<TSender, T1, T2>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Func<T1, T2, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2, T3>> WhenAnyValue<TSender, T1, T2, T3>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Func<T1, T2, T3, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2, T3, T4>> WhenAnyValue<TSender, T1, T2, T3, T4>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Func<T1, T2, T3, T4, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2, T3, T4, T5>> WhenAnyValue<TSender, T1, T2, T3, T4, T5>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Func<T1, T2, T3, T4, T5, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2, T3, T4, T5, T6>> WhenAnyValue<TSender, T1, T2, T3, T4, T5, T6>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Func<T1, T2, T3, T4, T5, T6, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2, T3, T4, T5, T6, T7>> WhenAnyValue<TSender, T1, T2, T3, T4, T5, T6, T7>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Func<T1, T2, T3, T4, T5, T6, T7, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11>> property11, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11>> property11, System.Linq.Expressions.Expression<System.Func<TSender, T12>> property12, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, ReactiveUI.IObservedChange<TSender, T8?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, ReactiveUI.IObservedChange<TSender, T8?>, ReactiveUI.IObservedChange<TSender, T9?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, ReactiveUI.IObservedChange<TSender, T8?>, ReactiveUI.IObservedChange<TSender, T9?>, ReactiveUI.IObservedChange<TSender, T10?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11?>> property11, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, ReactiveUI.IObservedChange<TSender, T8?>, ReactiveUI.IObservedChange<TSender, T9?>, ReactiveUI.IObservedChange<TSender, T10?>, ReactiveUI.IObservedChange<TSender, T11?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11?>> property11, System.Linq.Expressions.Expression<System.Func<TSender, T12?>> property12, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, ReactiveUI.IObservedChange<TSender, T8?>, ReactiveUI.IObservedChange<TSender, T9?>, ReactiveUI.IObservedChange<TSender, T10?>, ReactiveUI.IObservedChange<TSender, T11?>, ReactiveUI.IObservedChange<TSender, T12?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Linq.Expressions.Expression? property8, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Linq.Expressions.Expression? property8, System.Linq.Expressions.Expression? property9, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Linq.Expressions.Expression? property8, System.Linq.Expressions.Expression? property9, System.Linq.Expressions.Expression? property10, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Linq.Expressions.Expression? property8, System.Linq.Expressions.Expression? property9, System.Linq.Expressions.Expression? property10, System.Linq.Expressions.Expression? property11, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Linq.Expressions.Expression? property8, System.Linq.Expressions.Expression? property9, System.Linq.Expressions.Expression? property10, System.Linq.Expressions.Expression? property11, System.Linq.Expressions.Expression? property12, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, TRet?>> property1) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Func<T1?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?>> WhenAnyValue<TSender, T1, T2>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Func<T1?, T2?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?, T3?>> WhenAnyValue<TSender, T1, T2, T3>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Func<T1?, T2?, T3?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?, T3?, T4?>> WhenAnyValue<TSender, T1, T2, T3, T4>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Func<T1?, T2?, T3?, T4?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?, T3?, T4?, T5?>> WhenAnyValue<TSender, T1, T2, T3, T4, T5>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Func<T1?, T2?, T3?, T4?, T5?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?, T3?, T4?, T5?, T6?>> WhenAnyValue<TSender, T1, T2, T3, T4, T5, T6>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?, T3?, T4?, T5?, T6?, T7?>> WhenAnyValue<TSender, T1, T2, T3, T4, T5, T6, T7>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11?>> property11, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11?>> property11, System.Linq.Expressions.Expression<System.Func<TSender, T12?>> property12, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, TRet> selector) { }
     }
     public static class WhenAnyObservableMixin
     {
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs8)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs8)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs9)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs9)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs10)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs10)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs11)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs11)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs11, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs12)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs11, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs12)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Func<T1, T2, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Func<T1?, T2?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Func<T1, T2, T3, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Func<T1?, T2?, T3?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Func<T1, T2, T3, T4, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Func<T1?, T2?, T3?, T4?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Func<T1, T2, T3, T4, T5, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Func<T1?, T2?, T3?, T4?, T5?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Func<T1, T2, T3, T4, T5, T6, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Func<T1, T2, T3, T4, T5, T6, T7, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>>> obs8, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>?>> obs8, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>>> obs9, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>?>> obs9, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>>> obs10, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>?>> obs10, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T11>>> obs11, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>?>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T11>?>> obs11, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T11>>> obs11, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T12>>> obs12, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>?>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T11>?>> obs11, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T12>?>> obs12, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, TRet?> selector)
             where TSender :  class { }
     }
 }
diff --git a/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net5.0.approved.txt b/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net5.0.approved.txt
index 9f28cb433a..52a7d52fb1 100644
--- a/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net5.0.approved.txt
+++ b/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net5.0.approved.txt
@@ -221,7 +221,7 @@ namespace ReactiveUI
     }
     public interface IObservedChange<out TSender, out TValue>
     {
-        System.Linq.Expressions.Expression Expression { get; }
+        System.Linq.Expressions.Expression? Expression { get; }
         TSender Sender { get; }
         TValue Value { get; }
     }
@@ -312,7 +312,7 @@ namespace ReactiveUI
     }
     public interface ISetMethodBindingConverter : Splat.IEnableLogger
     {
-        int GetAffinityForObjects(System.Type fromType, System.Type toType);
+        int GetAffinityForObjects(System.Type? fromType, System.Type? toType);
         object? PerformSet(object? toTarget, object? newValue, object?[]? arguments);
     }
     public interface ISuspensionDriver
@@ -442,8 +442,8 @@ namespace ReactiveUI
     }
     public class ObservedChange<TSender, TValue> : ReactiveUI.IObservedChange<TSender, TValue>
     {
-        public ObservedChange(TSender sender, System.Linq.Expressions.Expression expression, TValue value) { }
-        public System.Linq.Expressions.Expression Expression { get; }
+        public ObservedChange(TSender sender, System.Linq.Expressions.Expression? expression, TValue value) { }
+        public System.Linq.Expressions.Expression? Expression { get; }
         public TSender Sender { get; }
         public TValue Value { get; }
     }
@@ -595,10 +595,10 @@ namespace ReactiveUI
     }
     public static class ReactiveNotifyPropertyChangedMixin
     {
-        public static System.IObservable<ReactiveUI.IObservedChange<TSender, TValue>> ObservableForProperty<TSender, TValue>(this TSender item, System.Linq.Expressions.Expression<System.Func<TSender, TValue>> property, bool beforeChange = false, bool skipInitial = true) { }
-        public static System.IObservable<TRet> ObservableForProperty<TSender, TValue, TRet>(this TSender item, System.Linq.Expressions.Expression<System.Func<TSender, TValue>> property, System.Func<TValue, TRet> selector, bool beforeChange = false)
+        public static System.IObservable<ReactiveUI.IObservedChange<TSender, TValue?>> ObservableForProperty<TSender, TValue>(this TSender? item, System.Linq.Expressions.Expression<System.Func<TSender, TValue?>> property, bool beforeChange = false, bool skipInitial = true) { }
+        public static System.IObservable<TRet> ObservableForProperty<TSender, TValue, TRet>(this TSender? item, System.Linq.Expressions.Expression<System.Func<TSender, TValue?>> property, System.Func<TValue?, TRet> selector, bool beforeChange = false)
             where TSender :  class { }
-        public static System.IObservable<ReactiveUI.IObservedChange<TSender, TValue>> SubscribeToExpressionChain<TSender, TValue>(this TSender source, System.Linq.Expressions.Expression expression, bool beforeChange = false, bool skipInitial = true, bool suppressWarnings = false) { }
+        public static System.IObservable<ReactiveUI.IObservedChange<TSender, TValue>> SubscribeToExpressionChain<TSender, TValue>(this TSender? source, System.Linq.Expressions.Expression? expression, bool beforeChange = false, bool skipInitial = true, bool suppressWarnings = false) { }
     }
     [System.Runtime.Serialization.DataContract]
     public class ReactiveObject : ReactiveUI.IHandleObservableErrors, ReactiveUI.IReactiveNotifyPropertyChanged<ReactiveUI.IReactiveObject>, ReactiveUI.IReactiveObject, Splat.IEnableLogger, System.ComponentModel.INotifyPropertyChanged, System.ComponentModel.INotifyPropertyChanging
@@ -654,15 +654,15 @@ namespace ReactiveUI
     }
     public static class Reflection
     {
-        public static string ExpressionToPropertyNames(System.Linq.Expressions.Expression expression) { }
+        public static string ExpressionToPropertyNames(System.Linq.Expressions.Expression? expression) { }
         public static System.Type GetEventArgsTypeForEvent(System.Type type, string eventName) { }
-        public static System.Func<object, object?[]?, object?>? GetValueFetcherForProperty(System.Reflection.MemberInfo? member) { }
-        public static System.Func<object, object?[]?, object?> GetValueFetcherOrThrow(System.Reflection.MemberInfo? member) { }
-        public static System.Action<object, object?, object?[]?> GetValueSetterForProperty(System.Reflection.MemberInfo? member) { }
-        public static System.Action<object, object?, object?[]?>? GetValueSetterOrThrow(System.Reflection.MemberInfo? member) { }
+        public static System.Func<object?, object?[]?, object?>? GetValueFetcherForProperty(System.Reflection.MemberInfo? member) { }
+        public static System.Func<object?, object?[]?, object?> GetValueFetcherOrThrow(System.Reflection.MemberInfo? member) { }
+        public static System.Action<object?, object?, object?[]?> GetValueSetterForProperty(System.Reflection.MemberInfo? member) { }
+        public static System.Action<object?, object?, object?[]?>? GetValueSetterOrThrow(System.Reflection.MemberInfo? member) { }
         public static bool IsStatic(this System.Reflection.PropertyInfo item) { }
         public static System.Type? ReallyFindType(string? type, bool throwOnFailure) { }
-        public static System.Linq.Expressions.Expression Rewrite(System.Linq.Expressions.Expression expression) { }
+        public static System.Linq.Expressions.Expression Rewrite(System.Linq.Expressions.Expression? expression) { }
         public static void ThrowIfMethodsNotOverloaded(string callingTypeName, object targetObject, params string[] methodsToCheck) { }
         public static bool TryGetAllValuesForPropertyChain(out ReactiveUI.IObservedChange<, >[] changeValues, object? current, System.Collections.Generic.IEnumerable<System.Linq.Expressions.Expression> expressionChain) { }
         public static bool TryGetValueForPropertyChain<TValue>(out TValue changeValue, object? current, System.Collections.Generic.IEnumerable<System.Linq.Expressions.Expression> expressionChain) { }
@@ -821,97 +821,97 @@ namespace ReactiveUI
     }
     public static class WhenAnyMixin
     {
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Func<ReactiveUI.IObservedChange<TSender, T1>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, ReactiveUI.IObservedChange<TSender, T8>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, ReactiveUI.IObservedChange<TSender, T8>, ReactiveUI.IObservedChange<TSender, T9>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, ReactiveUI.IObservedChange<TSender, T8>, ReactiveUI.IObservedChange<TSender, T9>, ReactiveUI.IObservedChange<TSender, T10>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11>> property11, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, ReactiveUI.IObservedChange<TSender, T8>, ReactiveUI.IObservedChange<TSender, T9>, ReactiveUI.IObservedChange<TSender, T10>, ReactiveUI.IObservedChange<TSender, T11>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11>> property11, System.Linq.Expressions.Expression<System.Func<TSender, T12>> property12, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, ReactiveUI.IObservedChange<TSender, T8>, ReactiveUI.IObservedChange<TSender, T9>, ReactiveUI.IObservedChange<TSender, T10>, ReactiveUI.IObservedChange<TSender, T11>, ReactiveUI.IObservedChange<TSender, T12>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Func<ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Linq.Expressions.Expression property8, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Linq.Expressions.Expression property8, System.Linq.Expressions.Expression property9, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Linq.Expressions.Expression property8, System.Linq.Expressions.Expression property9, System.Linq.Expressions.Expression property10, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Linq.Expressions.Expression property8, System.Linq.Expressions.Expression property9, System.Linq.Expressions.Expression property10, System.Linq.Expressions.Expression property11, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Linq.Expressions.Expression property8, System.Linq.Expressions.Expression property9, System.Linq.Expressions.Expression property10, System.Linq.Expressions.Expression property11, System.Linq.Expressions.Expression property12, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, TRet>> property1) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Func<T1, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2>> WhenAnyValue<TSender, T1, T2>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Func<T1, T2, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2, T3>> WhenAnyValue<TSender, T1, T2, T3>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Func<T1, T2, T3, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2, T3, T4>> WhenAnyValue<TSender, T1, T2, T3, T4>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Func<T1, T2, T3, T4, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2, T3, T4, T5>> WhenAnyValue<TSender, T1, T2, T3, T4, T5>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Func<T1, T2, T3, T4, T5, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2, T3, T4, T5, T6>> WhenAnyValue<TSender, T1, T2, T3, T4, T5, T6>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Func<T1, T2, T3, T4, T5, T6, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2, T3, T4, T5, T6, T7>> WhenAnyValue<TSender, T1, T2, T3, T4, T5, T6, T7>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Func<T1, T2, T3, T4, T5, T6, T7, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11>> property11, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11>> property11, System.Linq.Expressions.Expression<System.Func<TSender, T12>> property12, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, ReactiveUI.IObservedChange<TSender, T8?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, ReactiveUI.IObservedChange<TSender, T8?>, ReactiveUI.IObservedChange<TSender, T9?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, ReactiveUI.IObservedChange<TSender, T8?>, ReactiveUI.IObservedChange<TSender, T9?>, ReactiveUI.IObservedChange<TSender, T10?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11?>> property11, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, ReactiveUI.IObservedChange<TSender, T8?>, ReactiveUI.IObservedChange<TSender, T9?>, ReactiveUI.IObservedChange<TSender, T10?>, ReactiveUI.IObservedChange<TSender, T11?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11?>> property11, System.Linq.Expressions.Expression<System.Func<TSender, T12?>> property12, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, ReactiveUI.IObservedChange<TSender, T8?>, ReactiveUI.IObservedChange<TSender, T9?>, ReactiveUI.IObservedChange<TSender, T10?>, ReactiveUI.IObservedChange<TSender, T11?>, ReactiveUI.IObservedChange<TSender, T12?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Linq.Expressions.Expression? property8, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Linq.Expressions.Expression? property8, System.Linq.Expressions.Expression? property9, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Linq.Expressions.Expression? property8, System.Linq.Expressions.Expression? property9, System.Linq.Expressions.Expression? property10, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Linq.Expressions.Expression? property8, System.Linq.Expressions.Expression? property9, System.Linq.Expressions.Expression? property10, System.Linq.Expressions.Expression? property11, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Linq.Expressions.Expression? property8, System.Linq.Expressions.Expression? property9, System.Linq.Expressions.Expression? property10, System.Linq.Expressions.Expression? property11, System.Linq.Expressions.Expression? property12, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, TRet?>> property1) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Func<T1?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?>> WhenAnyValue<TSender, T1, T2>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Func<T1?, T2?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?, T3?>> WhenAnyValue<TSender, T1, T2, T3>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Func<T1?, T2?, T3?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?, T3?, T4?>> WhenAnyValue<TSender, T1, T2, T3, T4>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Func<T1?, T2?, T3?, T4?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?, T3?, T4?, T5?>> WhenAnyValue<TSender, T1, T2, T3, T4, T5>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Func<T1?, T2?, T3?, T4?, T5?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?, T3?, T4?, T5?, T6?>> WhenAnyValue<TSender, T1, T2, T3, T4, T5, T6>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?, T3?, T4?, T5?, T6?, T7?>> WhenAnyValue<TSender, T1, T2, T3, T4, T5, T6, T7>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11?>> property11, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11?>> property11, System.Linq.Expressions.Expression<System.Func<TSender, T12?>> property12, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, TRet> selector) { }
     }
     public static class WhenAnyObservableMixin
     {
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs8)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs8)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs9)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs9)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs10)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs10)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs11)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs11)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs11, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs12)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs11, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs12)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Func<T1, T2, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Func<T1?, T2?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Func<T1, T2, T3, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Func<T1?, T2?, T3?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Func<T1, T2, T3, T4, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Func<T1?, T2?, T3?, T4?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Func<T1, T2, T3, T4, T5, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Func<T1?, T2?, T3?, T4?, T5?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Func<T1, T2, T3, T4, T5, T6, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Func<T1, T2, T3, T4, T5, T6, T7, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>>> obs8, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>?>> obs8, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>>> obs9, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>?>> obs9, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>>> obs10, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>?>> obs10, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T11>>> obs11, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>?>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T11>?>> obs11, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T11>>> obs11, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T12>>> obs12, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>?>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T11>?>> obs11, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T12>?>> obs12, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, TRet?> selector)
             where TSender :  class { }
     }
 }
diff --git a/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.netcoreapp3.1.approved.txt b/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.netcoreapp3.1.approved.txt
index 1102562a15..fed6f25781 100644
--- a/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.netcoreapp3.1.approved.txt
+++ b/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.netcoreapp3.1.approved.txt
@@ -219,7 +219,7 @@ namespace ReactiveUI
     }
     public interface IObservedChange<out TSender, out TValue>
     {
-        System.Linq.Expressions.Expression Expression { get; }
+        System.Linq.Expressions.Expression? Expression { get; }
         TSender Sender { get; }
         TValue Value { get; }
     }
@@ -310,7 +310,7 @@ namespace ReactiveUI
     }
     public interface ISetMethodBindingConverter : Splat.IEnableLogger
     {
-        int GetAffinityForObjects(System.Type fromType, System.Type toType);
+        int GetAffinityForObjects(System.Type? fromType, System.Type? toType);
         object? PerformSet(object? toTarget, object? newValue, object?[]? arguments);
     }
     public interface ISuspensionDriver
@@ -440,8 +440,8 @@ namespace ReactiveUI
     }
     public class ObservedChange<TSender, TValue> : ReactiveUI.IObservedChange<TSender, TValue>
     {
-        public ObservedChange(TSender sender, System.Linq.Expressions.Expression expression, TValue value) { }
-        public System.Linq.Expressions.Expression Expression { get; }
+        public ObservedChange(TSender sender, System.Linq.Expressions.Expression? expression, TValue value) { }
+        public System.Linq.Expressions.Expression? Expression { get; }
         public TSender Sender { get; }
         public TValue Value { get; }
     }
@@ -593,10 +593,10 @@ namespace ReactiveUI
     }
     public static class ReactiveNotifyPropertyChangedMixin
     {
-        public static System.IObservable<ReactiveUI.IObservedChange<TSender, TValue>> ObservableForProperty<TSender, TValue>(this TSender item, System.Linq.Expressions.Expression<System.Func<TSender, TValue>> property, bool beforeChange = false, bool skipInitial = true) { }
-        public static System.IObservable<TRet> ObservableForProperty<TSender, TValue, TRet>(this TSender item, System.Linq.Expressions.Expression<System.Func<TSender, TValue>> property, System.Func<TValue, TRet> selector, bool beforeChange = false)
+        public static System.IObservable<ReactiveUI.IObservedChange<TSender, TValue?>> ObservableForProperty<TSender, TValue>(this TSender? item, System.Linq.Expressions.Expression<System.Func<TSender, TValue?>> property, bool beforeChange = false, bool skipInitial = true) { }
+        public static System.IObservable<TRet> ObservableForProperty<TSender, TValue, TRet>(this TSender? item, System.Linq.Expressions.Expression<System.Func<TSender, TValue?>> property, System.Func<TValue?, TRet> selector, bool beforeChange = false)
             where TSender :  class { }
-        public static System.IObservable<ReactiveUI.IObservedChange<TSender, TValue>> SubscribeToExpressionChain<TSender, TValue>(this TSender source, System.Linq.Expressions.Expression expression, bool beforeChange = false, bool skipInitial = true, bool suppressWarnings = false) { }
+        public static System.IObservable<ReactiveUI.IObservedChange<TSender, TValue>> SubscribeToExpressionChain<TSender, TValue>(this TSender? source, System.Linq.Expressions.Expression? expression, bool beforeChange = false, bool skipInitial = true, bool suppressWarnings = false) { }
     }
     [System.Runtime.Serialization.DataContract]
     public class ReactiveObject : ReactiveUI.IHandleObservableErrors, ReactiveUI.IReactiveNotifyPropertyChanged<ReactiveUI.IReactiveObject>, ReactiveUI.IReactiveObject, Splat.IEnableLogger, System.ComponentModel.INotifyPropertyChanged, System.ComponentModel.INotifyPropertyChanging
@@ -652,15 +652,15 @@ namespace ReactiveUI
     }
     public static class Reflection
     {
-        public static string ExpressionToPropertyNames(System.Linq.Expressions.Expression expression) { }
+        public static string ExpressionToPropertyNames(System.Linq.Expressions.Expression? expression) { }
         public static System.Type GetEventArgsTypeForEvent(System.Type type, string eventName) { }
-        public static System.Func<object, object?[]?, object?>? GetValueFetcherForProperty(System.Reflection.MemberInfo? member) { }
-        public static System.Func<object, object?[]?, object?> GetValueFetcherOrThrow(System.Reflection.MemberInfo? member) { }
-        public static System.Action<object, object?, object?[]?> GetValueSetterForProperty(System.Reflection.MemberInfo? member) { }
-        public static System.Action<object, object?, object?[]?>? GetValueSetterOrThrow(System.Reflection.MemberInfo? member) { }
+        public static System.Func<object?, object?[]?, object?>? GetValueFetcherForProperty(System.Reflection.MemberInfo? member) { }
+        public static System.Func<object?, object?[]?, object?> GetValueFetcherOrThrow(System.Reflection.MemberInfo? member) { }
+        public static System.Action<object?, object?, object?[]?> GetValueSetterForProperty(System.Reflection.MemberInfo? member) { }
+        public static System.Action<object?, object?, object?[]?>? GetValueSetterOrThrow(System.Reflection.MemberInfo? member) { }
         public static bool IsStatic(this System.Reflection.PropertyInfo item) { }
         public static System.Type? ReallyFindType(string? type, bool throwOnFailure) { }
-        public static System.Linq.Expressions.Expression Rewrite(System.Linq.Expressions.Expression expression) { }
+        public static System.Linq.Expressions.Expression Rewrite(System.Linq.Expressions.Expression? expression) { }
         public static void ThrowIfMethodsNotOverloaded(string callingTypeName, object targetObject, params string[] methodsToCheck) { }
         public static bool TryGetAllValuesForPropertyChain(out ReactiveUI.IObservedChange<, >[] changeValues, object? current, System.Collections.Generic.IEnumerable<System.Linq.Expressions.Expression> expressionChain) { }
         public static bool TryGetValueForPropertyChain<TValue>(out TValue changeValue, object? current, System.Collections.Generic.IEnumerable<System.Linq.Expressions.Expression> expressionChain) { }
@@ -819,97 +819,97 @@ namespace ReactiveUI
     }
     public static class WhenAnyMixin
     {
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Func<ReactiveUI.IObservedChange<TSender, T1>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, ReactiveUI.IObservedChange<TSender, T8>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, ReactiveUI.IObservedChange<TSender, T8>, ReactiveUI.IObservedChange<TSender, T9>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, ReactiveUI.IObservedChange<TSender, T8>, ReactiveUI.IObservedChange<TSender, T9>, ReactiveUI.IObservedChange<TSender, T10>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11>> property11, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, ReactiveUI.IObservedChange<TSender, T8>, ReactiveUI.IObservedChange<TSender, T9>, ReactiveUI.IObservedChange<TSender, T10>, ReactiveUI.IObservedChange<TSender, T11>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11>> property11, System.Linq.Expressions.Expression<System.Func<TSender, T12>> property12, System.Func<ReactiveUI.IObservedChange<TSender, T1>, ReactiveUI.IObservedChange<TSender, T2>, ReactiveUI.IObservedChange<TSender, T3>, ReactiveUI.IObservedChange<TSender, T4>, ReactiveUI.IObservedChange<TSender, T5>, ReactiveUI.IObservedChange<TSender, T6>, ReactiveUI.IObservedChange<TSender, T7>, ReactiveUI.IObservedChange<TSender, T8>, ReactiveUI.IObservedChange<TSender, T9>, ReactiveUI.IObservedChange<TSender, T10>, ReactiveUI.IObservedChange<TSender, T11>, ReactiveUI.IObservedChange<TSender, T12>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Func<ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Linq.Expressions.Expression property8, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Linq.Expressions.Expression property8, System.Linq.Expressions.Expression property9, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Linq.Expressions.Expression property8, System.Linq.Expressions.Expression property9, System.Linq.Expressions.Expression property10, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Linq.Expressions.Expression property8, System.Linq.Expressions.Expression property9, System.Linq.Expressions.Expression property10, System.Linq.Expressions.Expression property11, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyDynamic<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression property1, System.Linq.Expressions.Expression property2, System.Linq.Expressions.Expression property3, System.Linq.Expressions.Expression property4, System.Linq.Expressions.Expression property5, System.Linq.Expressions.Expression property6, System.Linq.Expressions.Expression property7, System.Linq.Expressions.Expression property8, System.Linq.Expressions.Expression property9, System.Linq.Expressions.Expression property10, System.Linq.Expressions.Expression property11, System.Linq.Expressions.Expression property12, System.Func<ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, ReactiveUI.IObservedChange<TSender, object>, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, TRet>> property1) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Func<T1, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2>> WhenAnyValue<TSender, T1, T2>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Func<T1, T2, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2, T3>> WhenAnyValue<TSender, T1, T2, T3>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Func<T1, T2, T3, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2, T3, T4>> WhenAnyValue<TSender, T1, T2, T3, T4>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Func<T1, T2, T3, T4, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2, T3, T4, T5>> WhenAnyValue<TSender, T1, T2, T3, T4, T5>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Func<T1, T2, T3, T4, T5, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2, T3, T4, T5, T6>> WhenAnyValue<TSender, T1, T2, T3, T4, T5, T6>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Func<T1, T2, T3, T4, T5, T6, TRet> selector) { }
-        public static System.IObservable<System.ValueTuple<T1, T2, T3, T4, T5, T6, T7>> WhenAnyValue<TSender, T1, T2, T3, T4, T5, T6, T7>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Func<T1, T2, T3, T4, T5, T6, T7, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11>> property11, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, TRet> selector) { }
-        public static System.IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, T1>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11>> property11, System.Linq.Expressions.Expression<System.Func<TSender, T12>> property12, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, ReactiveUI.IObservedChange<TSender, T8?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, ReactiveUI.IObservedChange<TSender, T8?>, ReactiveUI.IObservedChange<TSender, T9?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, ReactiveUI.IObservedChange<TSender, T8?>, ReactiveUI.IObservedChange<TSender, T9?>, ReactiveUI.IObservedChange<TSender, T10?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11?>> property11, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, ReactiveUI.IObservedChange<TSender, T8?>, ReactiveUI.IObservedChange<TSender, T9?>, ReactiveUI.IObservedChange<TSender, T10?>, ReactiveUI.IObservedChange<TSender, T11?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11?>> property11, System.Linq.Expressions.Expression<System.Func<TSender, T12?>> property12, System.Func<ReactiveUI.IObservedChange<TSender, T1?>, ReactiveUI.IObservedChange<TSender, T2?>, ReactiveUI.IObservedChange<TSender, T3?>, ReactiveUI.IObservedChange<TSender, T4?>, ReactiveUI.IObservedChange<TSender, T5?>, ReactiveUI.IObservedChange<TSender, T6?>, ReactiveUI.IObservedChange<TSender, T7?>, ReactiveUI.IObservedChange<TSender, T8?>, ReactiveUI.IObservedChange<TSender, T9?>, ReactiveUI.IObservedChange<TSender, T10?>, ReactiveUI.IObservedChange<TSender, T11?>, ReactiveUI.IObservedChange<TSender, T12?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Linq.Expressions.Expression? property8, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Linq.Expressions.Expression? property8, System.Linq.Expressions.Expression? property9, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Linq.Expressions.Expression? property8, System.Linq.Expressions.Expression? property9, System.Linq.Expressions.Expression? property10, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Linq.Expressions.Expression? property8, System.Linq.Expressions.Expression? property9, System.Linq.Expressions.Expression? property10, System.Linq.Expressions.Expression? property11, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression? property1, System.Linq.Expressions.Expression? property2, System.Linq.Expressions.Expression? property3, System.Linq.Expressions.Expression? property4, System.Linq.Expressions.Expression? property5, System.Linq.Expressions.Expression? property6, System.Linq.Expressions.Expression? property7, System.Linq.Expressions.Expression? property8, System.Linq.Expressions.Expression? property9, System.Linq.Expressions.Expression? property10, System.Linq.Expressions.Expression? property11, System.Linq.Expressions.Expression? property12, System.Func<ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, ReactiveUI.IObservedChange<TSender?, object?>, TRet?> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, TRet?>> property1) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Func<T1?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?>> WhenAnyValue<TSender, T1, T2>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Func<T1?, T2?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?, T3?>> WhenAnyValue<TSender, T1, T2, T3>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Func<T1?, T2?, T3?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?, T3?, T4?>> WhenAnyValue<TSender, T1, T2, T3, T4>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Func<T1?, T2?, T3?, T4?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?, T3?, T4?, T5?>> WhenAnyValue<TSender, T1, T2, T3, T4, T5>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Func<T1?, T2?, T3?, T4?, T5?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?, T3?, T4?, T5?, T6?>> WhenAnyValue<TSender, T1, T2, T3, T4, T5, T6>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, TRet> selector) { }
+        public static System.IObservable<System.ValueTuple<T1?, T2?, T3?, T4?, T5?, T6?, T7?>> WhenAnyValue<TSender, T1, T2, T3, T4, T5, T6, T7>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11?>> property11, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, TRet> selector) { }
+        public static System.IObservable<TRet?> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, T1?>> property1, System.Linq.Expressions.Expression<System.Func<TSender, T2?>> property2, System.Linq.Expressions.Expression<System.Func<TSender, T3?>> property3, System.Linq.Expressions.Expression<System.Func<TSender, T4?>> property4, System.Linq.Expressions.Expression<System.Func<TSender, T5?>> property5, System.Linq.Expressions.Expression<System.Func<TSender, T6?>> property6, System.Linq.Expressions.Expression<System.Func<TSender, T7?>> property7, System.Linq.Expressions.Expression<System.Func<TSender, T8?>> property8, System.Linq.Expressions.Expression<System.Func<TSender, T9?>> property9, System.Linq.Expressions.Expression<System.Func<TSender, T10?>> property10, System.Linq.Expressions.Expression<System.Func<TSender, T11?>> property11, System.Linq.Expressions.Expression<System.Func<TSender, T12?>> property12, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, TRet> selector) { }
     }
     public static class WhenAnyObservableMixin
     {
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs8)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs8)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs9)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs9)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs10)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs10)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs11)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs11)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs11, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>>> obs12)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs11, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<TRet>?>> obs12)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Func<T1, T2, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Func<T1?, T2?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Func<T1, T2, T3, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Func<T1?, T2?, T3?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Func<T1, T2, T3, T4, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Func<T1?, T2?, T3?, T4?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Func<T1, T2, T3, T4, T5, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Func<T1?, T2?, T3?, T4?, T5?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Func<T1, T2, T3, T4, T5, T6, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Func<T1, T2, T3, T4, T5, T6, T7, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>>> obs8, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>?>> obs8, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>>> obs9, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>?>> obs9, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>>> obs10, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>?>> obs10, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T11>>> obs11, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>?>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T11>?>> obs11, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, TRet?> selector)
             where TSender :  class { }
-        public static System.IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T11>>> obs11, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T12>>> obs12, System.Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, TRet> selector)
+        public static System.IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender? sender, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T1>?>> obs1, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T2>?>> obs2, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T3>?>> obs3, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T4>?>> obs4, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T5>?>> obs5, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T6>?>> obs6, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T7>?>> obs7, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T8>?>> obs8, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T9>?>> obs9, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T10>?>> obs10, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T11>?>> obs11, System.Linq.Expressions.Expression<System.Func<TSender, System.IObservable<T12>?>> obs12, System.Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, TRet?> selector)
             where TSender :  class { }
     }
 }
diff --git a/src/ReactiveUI.Tests/Commands/ReactiveCommandTest.cs b/src/ReactiveUI.Tests/Commands/ReactiveCommandTest.cs
index 4079c50981..e15a921427 100644
--- a/src/ReactiveUI.Tests/Commands/ReactiveCommandTest.cs
+++ b/src/ReactiveUI.Tests/Commands/ReactiveCommandTest.cs
@@ -72,7 +72,7 @@ public void CanExecuteIsAvailableViaICommand()
         public void CanExecuteIsBehavioral()
         {
             ReactiveCommand<Unit, IObservable<Unit>> fixture = ReactiveCommand.Create(() => Observables.Unit, outputScheduler: ImmediateScheduler.Instance);
-            fixture.CanExecute.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<bool> canExecute).Subscribe();
+            fixture.CanExecute.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var canExecute).Subscribe();
 
             Assert.Equal(1, canExecute.Count);
             Assert.True(canExecute[0]);
@@ -86,9 +86,9 @@ public void CanExecuteIsFalseIfAlreadyExecuting() =>
             new TestScheduler().With(
                 scheduler =>
                 {
-                    IObservable<Unit> execute = Observables.Unit.Delay(TimeSpan.FromSeconds(1), scheduler);
+                    var execute = Observables.Unit.Delay(TimeSpan.FromSeconds(1), scheduler);
                     ReactiveCommand<Unit, Unit> fixture = ReactiveCommand.CreateFromObservable(() => execute, outputScheduler: scheduler);
-                    fixture.CanExecute.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<bool> canExecute).Subscribe();
+                    fixture.CanExecute.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var canExecute).Subscribe();
 
                     fixture.Execute().Subscribe();
                     scheduler.AdvanceByMs(100);
@@ -110,7 +110,7 @@ public void CanExecuteIsFalseIfCallerDictatesAsSuch()
         {
             Subject<bool> canExecuteSubject = new();
             ReactiveCommand<Unit, IObservable<Unit>> fixture = ReactiveCommand.Create(() => Observables.Unit, canExecuteSubject, ImmediateScheduler.Instance);
-            fixture.CanExecute.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<bool> canExecute).Subscribe();
+            fixture.CanExecute.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var canExecute).Subscribe();
 
             canExecuteSubject.OnNext(true);
             canExecuteSubject.OnNext(false);
@@ -145,7 +145,7 @@ public void CanExecuteOnlyTicksDistinctValues()
         {
             Subject<bool> canExecuteSubject = new();
             ReactiveCommand<Unit, IObservable<Unit>> fixture = ReactiveCommand.Create(() => Observables.Unit, canExecuteSubject, ImmediateScheduler.Instance);
-            fixture.CanExecute.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<bool> canExecute).Subscribe();
+            fixture.CanExecute.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var canExecute).Subscribe();
 
             canExecuteSubject.OnNext(false);
             canExecuteSubject.OnNext(false);
@@ -167,7 +167,7 @@ public void CanExecuteTicksFailuresThroughThrownExceptions()
         {
             Subject<bool> canExecuteSubject = new();
             ReactiveCommand<Unit, IObservable<Unit>> fixture = ReactiveCommand.Create(() => Observables.Unit, canExecuteSubject, ImmediateScheduler.Instance);
-            fixture.ThrownExceptions.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<Exception> thrownExceptions).Subscribe();
+            fixture.ThrownExceptions.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var thrownExceptions).Subscribe();
 
             canExecuteSubject.OnError(new InvalidOperationException("oops"));
 
@@ -182,7 +182,7 @@ public void CanExecuteTicksFailuresThroughThrownExceptions()
         public void CreateTaskFacilitatesTPLIntegration()
         {
             ReactiveCommand<Unit, int> fixture = ReactiveCommand.CreateFromTask(() => Task.FromResult(13), outputScheduler: ImmediateScheduler.Instance);
-            fixture.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<int> results).Subscribe();
+            fixture.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var results).Subscribe();
 
             fixture.Execute().Subscribe();
 
@@ -197,7 +197,7 @@ public void CreateTaskFacilitatesTPLIntegration()
         public void CreateTaskFacilitatesTPLIntegrationWithParameter()
         {
             ReactiveCommand<int, int> fixture = ReactiveCommand.CreateFromTask<int, int>(param => Task.FromResult(param + 1), outputScheduler: ImmediateScheduler.Instance);
-            fixture.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<int> results).Subscribe();
+            fixture.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var results).Subscribe();
 
             fixture.Execute(3).Subscribe();
             fixture.Execute(41).Subscribe();
@@ -253,12 +253,12 @@ public void ExecuteCanBeCancelled() =>
             new TestScheduler().With(
                 scheduler =>
                 {
-                    IObservable<Unit> execute = Observables.Unit.Delay(TimeSpan.FromSeconds(1), scheduler);
+                    var execute = Observables.Unit.Delay(TimeSpan.FromSeconds(1), scheduler);
                     ReactiveCommand<Unit, Unit> fixture = ReactiveCommand.CreateFromObservable(() => execute, outputScheduler: scheduler);
-                    fixture.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<Unit> executed).Subscribe();
+                    fixture.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var executed).Subscribe();
 
-                    IDisposable sub1 = fixture.Execute().Subscribe();
-                    IDisposable sub2 = fixture.Execute().Subscribe();
+                    var sub1 = fixture.Execute().Subscribe();
+                    var sub2 = fixture.Execute().Subscribe();
                     scheduler.AdvanceByMs(999);
 
                     Assert.True(fixture.IsExecuting.FirstAsync().Wait());
@@ -277,7 +277,7 @@ public void ExecuteCanBeCancelled() =>
         public void ExecuteCanTickThroughMultipleResults()
         {
             ReactiveCommand<Unit, int> fixture = ReactiveCommand.CreateFromObservable(() => new[] { 1, 2, 3 }.ToObservable(), outputScheduler: ImmediateScheduler.Instance);
-            fixture.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<int> results).Subscribe();
+            fixture.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var results).Subscribe();
 
             fixture.Execute().Subscribe();
 
@@ -295,17 +295,17 @@ public void ExecuteFacilitatesAnyNumberOfInFlightExecutions() =>
             new TestScheduler().With(
                 scheduler =>
                 {
-                    IObservable<Unit> execute = Observables.Unit.Delay(TimeSpan.FromMilliseconds(500), scheduler);
+                    var execute = Observables.Unit.Delay(TimeSpan.FromMilliseconds(500), scheduler);
                     ReactiveCommand<Unit, Unit> fixture = ReactiveCommand.CreateFromObservable(() => execute, outputScheduler: scheduler);
-                    fixture.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<Unit> executed).Subscribe();
+                    fixture.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var executed).Subscribe();
 
-                    IDisposable sub1 = fixture.Execute().Subscribe();
-                    IDisposable sub2 = fixture.Execute().Subscribe();
+                    var sub1 = fixture.Execute().Subscribe();
+                    var sub2 = fixture.Execute().Subscribe();
                     scheduler.AdvanceByMs(100);
 
-                    IDisposable sub3 = fixture.Execute().Subscribe();
+                    var sub3 = fixture.Execute().Subscribe();
                     scheduler.AdvanceByMs(200);
-                    IDisposable sub4 = fixture.Execute().Subscribe();
+                    var sub4 = fixture.Execute().Subscribe();
                     scheduler.AdvanceByMs(100);
 
                     Assert.True(fixture.IsExecuting.FirstAsync().Wait());
@@ -330,7 +330,7 @@ public void ExecuteFacilitatesAnyNumberOfInFlightExecutions() =>
         [Fact]
         public void ExecuteIsAvailableViaICommand()
         {
-            bool executed = false;
+            var executed = false;
             ICommand fixture = ReactiveCommand.Create(
                                                       () =>
                                                       {
@@ -375,8 +375,8 @@ public void ExecutePassesThroughParameter()
         public void ExecuteReenablesExecutionEvenAfterFailure()
         {
             ReactiveCommand<Unit, Unit> fixture = ReactiveCommand.CreateFromObservable(() => Observable.Throw<Unit>(new InvalidOperationException("oops")), outputScheduler: ImmediateScheduler.Instance);
-            fixture.CanExecute.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<bool> canExecute).Subscribe();
-            fixture.ThrownExceptions.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<Exception> thrownExceptions).Subscribe();
+            fixture.CanExecute.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var canExecute).Subscribe();
+            fixture.ThrownExceptions.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var thrownExceptions).Subscribe();
 
             fixture.Execute().Subscribe(_ => { }, _ => { });
 
@@ -397,9 +397,9 @@ public void ExecuteResultIsDeliveredOnSpecifiedScheduler() =>
             new TestScheduler().With(
                 scheduler =>
                 {
-                    IObservable<Unit> execute = Observables.Unit;
+                    var execute = Observables.Unit;
                     ReactiveCommand<Unit, Unit> fixture = ReactiveCommand.CreateFromObservable(() => execute, outputScheduler: scheduler);
-                    bool executed = false;
+                    var executed = false;
 
                     fixture.Execute().Subscribe(_ => executed = true);
 
@@ -443,7 +443,7 @@ public void ExecuteTicksAnyLambdaException()
         public void ExecuteTicksErrorsThroughThrownExceptions()
         {
             ReactiveCommand<Unit, Unit> fixture = ReactiveCommand.CreateFromObservable(() => Observable.Throw<Unit>(new InvalidOperationException("oops")), outputScheduler: ImmediateScheduler.Instance);
-            fixture.ThrownExceptions.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<Exception> thrownExceptions).Subscribe();
+            fixture.ThrownExceptions.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var thrownExceptions).Subscribe();
 
             fixture.Execute().Subscribe(_ => { }, _ => { });
 
@@ -458,7 +458,7 @@ public void ExecuteTicksErrorsThroughThrownExceptions()
         public void ExecuteTicksLambdaErrorsThroughThrownExceptions()
         {
             ReactiveCommand<Unit, Unit> fixture = ReactiveCommand.CreateFromObservable<Unit>(() => throw new InvalidOperationException("oops"), outputScheduler: ImmediateScheduler.Instance);
-            fixture.ThrownExceptions.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<Exception> thrownExceptions).Subscribe();
+            fixture.ThrownExceptions.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var thrownExceptions).Subscribe();
 
             fixture.Execute().Subscribe(_ => { }, _ => { });
 
@@ -473,9 +473,9 @@ public void ExecuteTicksLambdaErrorsThroughThrownExceptions()
         [Fact]
         public void ExecuteTicksThroughTheResult()
         {
-            int num = 0;
+            var num = 0;
             ReactiveCommand<Unit, int> fixture = ReactiveCommand.CreateFromObservable(() => Observable.Return(num), outputScheduler: ImmediateScheduler.Instance);
-            fixture.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<int> results).Subscribe();
+            fixture.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var results).Subscribe();
 
             num = 1;
             fixture.Execute().Subscribe();
@@ -497,7 +497,7 @@ public void ExecuteTicksThroughTheResult()
         public void ExecuteViaICommandThrowsIfParameterTypeIsIncorrect()
         {
             ICommand fixture = ReactiveCommand.Create<int>(_ => { }, outputScheduler: ImmediateScheduler.Instance);
-            InvalidOperationException ex = Assert.Throws<InvalidOperationException>(() => fixture.Execute("foo"));
+            var ex = Assert.Throws<InvalidOperationException>(() => fixture.Execute("foo"));
             Assert.Equal("Command requires parameters of type System.Int32, but received parameter of type System.String.", ex.Message);
 
             fixture = ReactiveCommand.Create<string>(_ => { });
@@ -527,7 +527,7 @@ public void ExecuteViaICommandWorksWithNullableTypes()
         [Fact]
         public void InvokeCommandAgainstICommandInTargetInvokesTheCommand()
         {
-            int executionCount = 0;
+            var executionCount = 0;
             ICommandHolder fixture = new();
             Subject<Unit> source = new();
             source.InvokeCommand(fixture, x => x.TheCommand!);
@@ -580,7 +580,7 @@ public void InvokeCommandAgainstICommandInNullableTargetPassesTheSpecifiedValueT
         [Fact]
         public void InvokeCommandAgainstICommandInTargetRespectsCanExecute()
         {
-            bool executed = false;
+            var executed = false;
             BehaviorSubject<bool> canExecute = new(false);
             ICommandHolder fixture = new();
             Subject<Unit> source = new();
@@ -601,7 +601,7 @@ public void InvokeCommandAgainstICommandInTargetRespectsCanExecute()
         [Fact]
         public void InvokeCommandAgainstICommandInNullableTargetRespectsCanExecute()
         {
-            bool executed = false;
+            var executed = false;
             BehaviorSubject<bool> canExecute = new(false);
             ICommandHolder? fixture = new();
             Subject<Unit> source = new();
@@ -622,7 +622,7 @@ public void InvokeCommandAgainstICommandInNullableTargetRespectsCanExecute()
         [Fact]
         public void InvokeCommandAgainstICommandInTargetRespectsCanExecuteWindow()
         {
-            bool executed = false;
+            var executed = false;
             BehaviorSubject<bool> canExecute = new(false);
             ICommandHolder fixture = new();
             Subject<Unit> source = new();
@@ -644,7 +644,7 @@ public void InvokeCommandAgainstICommandInTargetRespectsCanExecuteWindow()
         [Fact]
         public void InvokeCommandAgainstICommandInTargetSwallowsExceptions()
         {
-            int count = 0;
+            var count = 0;
             ICommandHolder fixture = new();
             ReactiveCommand<Unit, Unit> command = ReactiveCommand.Create(
                                                  () =>
@@ -670,7 +670,7 @@ public void InvokeCommandAgainstICommandInTargetSwallowsExceptions()
         [Fact]
         public void InvokeCommandAgainstICommandInvokesTheCommand()
         {
-            int executionCount = 0;
+            var executionCount = 0;
             ICommand fixture = ReactiveCommand.Create(() => ++executionCount, outputScheduler: ImmediateScheduler.Instance);
             Subject<Unit> source = new();
             source.InvokeCommand(fixture);
@@ -688,7 +688,7 @@ public void InvokeCommandAgainstICommandInvokesTheCommand()
         [Fact]
         public void InvokeCommandAgainstNullableICommandInvokesTheCommand()
         {
-            int executionCount = 0;
+            var executionCount = 0;
             ICommand? fixture = ReactiveCommand.Create(() => ++executionCount, outputScheduler: ImmediateScheduler.Instance);
             Subject<Unit> source = new();
             source.InvokeCommand(fixture);
@@ -721,7 +721,7 @@ public void InvokeCommandAgainstICommandPassesTheSpecifiedValueToCanExecuteAndEx
         [Fact]
         public void InvokeCommandAgainstICommandRespectsCanExecute()
         {
-            bool executed = false;
+            var executed = false;
             BehaviorSubject<bool> canExecute = new(false);
             ICommand fixture = ReactiveCommand.Create(() => executed = true, canExecute, ImmediateScheduler.Instance);
             Subject<Unit> source = new();
@@ -741,7 +741,7 @@ public void InvokeCommandAgainstICommandRespectsCanExecute()
         [Fact]
         public void InvokeCommandAgainstICommandRespectsCanExecuteWindow()
         {
-            bool executed = false;
+            var executed = false;
             BehaviorSubject<bool> canExecute = new(false);
             ICommand fixture = ReactiveCommand.Create(() => executed = true, canExecute, ImmediateScheduler.Instance);
             Subject<Unit> source = new();
@@ -762,7 +762,7 @@ public void InvokeCommandAgainstICommandRespectsCanExecuteWindow()
         [Fact]
         public void InvokeCommandAgainstICommandSwallowsExceptions()
         {
-            int count = 0;
+            var count = 0;
             ReactiveCommand<Unit, Unit> fixture = ReactiveCommand.Create(
                                                  () =>
                                                  {
@@ -786,7 +786,7 @@ public void InvokeCommandAgainstICommandSwallowsExceptions()
         [Fact]
         public void InvokeCommandAgainstReactiveCommandInTargetInvokesTheCommand()
         {
-            int executionCount = 0;
+            var executionCount = 0;
             ReactiveCommandHolder fixture = new();
             Subject<int> source = new();
             source.InvokeCommand(fixture, x => x.TheCommand!);
@@ -805,7 +805,7 @@ public void InvokeCommandAgainstReactiveCommandInTargetInvokesTheCommand()
         [Fact]
         public void InvokeCommandAgainstReactiveCommandInTargetPassesTheSpecifiedValueToExecute()
         {
-            int executeReceived = 0;
+            var executeReceived = 0;
             ReactiveCommandHolder fixture = new();
             Subject<int> source = new();
             source.InvokeCommand(fixture, x => x.TheCommand!);
@@ -821,7 +821,7 @@ public void InvokeCommandAgainstReactiveCommandInTargetPassesTheSpecifiedValueTo
         [Fact]
         public void InvokeCommandAgainstReactiveCommandInTargetRespectsCanExecute()
         {
-            bool executed = false;
+            var executed = false;
             BehaviorSubject<bool> canExecute = new(false);
             ReactiveCommandHolder fixture = new();
             Subject<int> source = new();
@@ -842,7 +842,7 @@ public void InvokeCommandAgainstReactiveCommandInTargetRespectsCanExecute()
         [Fact]
         public void InvokeCommandAgainstReactiveCommandInTargetRespectsCanExecuteWindow()
         {
-            bool executed = false;
+            var executed = false;
             BehaviorSubject<bool> canExecute = new(false);
             ReactiveCommandHolder fixture = new();
             Subject<int> source = new();
@@ -864,7 +864,7 @@ public void InvokeCommandAgainstReactiveCommandInTargetRespectsCanExecuteWindow(
         [Fact]
         public void InvokeCommandAgainstReactiveCommandInTargetSwallowsExceptions()
         {
-            int count = 0;
+            var count = 0;
             ReactiveCommandHolder fixture = new()
             {
                 TheCommand = ReactiveCommand.Create<int>(
@@ -891,7 +891,7 @@ public void InvokeCommandAgainstReactiveCommandInTargetSwallowsExceptions()
         [Fact]
         public void InvokeCommandAgainstReactiveCommandInvokesTheCommand()
         {
-            int executionCount = 0;
+            var executionCount = 0;
             ReactiveCommand<Unit, int> fixture = ReactiveCommand.Create(() => ++executionCount, outputScheduler: ImmediateScheduler.Instance);
             Subject<Unit> source = new();
             source.InvokeCommand(fixture);
@@ -909,7 +909,7 @@ public void InvokeCommandAgainstReactiveCommandInvokesTheCommand()
         [Fact]
         public void InvokeCommandAgainstReactiveCommandPassesTheSpecifiedValueToExecute()
         {
-            int executeReceived = 0;
+            var executeReceived = 0;
             ReactiveCommand<int, Unit> fixture = ReactiveCommand.Create<int>(x => executeReceived = x, outputScheduler: ImmediateScheduler.Instance);
             Subject<int> source = new();
             source.InvokeCommand(fixture);
@@ -924,7 +924,7 @@ public void InvokeCommandAgainstReactiveCommandPassesTheSpecifiedValueToExecute(
         [Fact]
         public void InvokeCommandAgainstReactiveCommandRespectsCanExecute()
         {
-            bool executed = false;
+            var executed = false;
             BehaviorSubject<bool> canExecute = new(false);
             ReactiveCommand<Unit, bool> fixture = ReactiveCommand.Create(() => executed = true, canExecute, ImmediateScheduler.Instance);
             Subject<Unit> source = new();
@@ -944,7 +944,7 @@ public void InvokeCommandAgainstReactiveCommandRespectsCanExecute()
         [Fact]
         public void InvokeCommandAgainstReactiveCommandRespectsCanExecuteWindow()
         {
-            bool executed = false;
+            var executed = false;
             BehaviorSubject<bool> canExecute = new(false);
             ReactiveCommand<Unit, bool> fixture = ReactiveCommand.Create(() => executed = true, canExecute, outputScheduler: ImmediateScheduler.Instance);
             Subject<Unit> source = new();
@@ -965,7 +965,7 @@ public void InvokeCommandAgainstReactiveCommandRespectsCanExecuteWindow()
         [Fact]
         public void InvokeCommandAgainstReactiveCommandSwallowsExceptions()
         {
-            int count = 0;
+            var count = 0;
             ReactiveCommand<Unit, Unit> fixture = ReactiveCommand.Create(
                                                  () =>
                                                  {
@@ -989,9 +989,9 @@ public void InvokeCommandAgainstReactiveCommandSwallowsExceptions()
         [Fact]
         public void InvokeCommandWorksEvenIfTheSourceIsCold()
         {
-            int executionCount = 0;
+            var executionCount = 0;
             ReactiveCommand<Unit, int> fixture = ReactiveCommand.Create(() => ++executionCount, outputScheduler: ImmediateScheduler.Instance);
-            IObservable<Unit> source = Observable.Return(Unit.Default);
+            var source = Observable.Return(Unit.Default);
             source.InvokeCommand(fixture);
 
             Assert.Equal(1, executionCount);
@@ -1004,7 +1004,7 @@ public void InvokeCommandWorksEvenIfTheSourceIsCold()
         public void IsExecutingIsBehavioral()
         {
             ReactiveCommand<Unit, IObservable<Unit>> fixture = ReactiveCommand.Create(() => Observables.Unit, outputScheduler: ImmediateScheduler.Instance);
-            fixture.IsExecuting.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<bool> isExecuting).Subscribe();
+            fixture.IsExecuting.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var isExecuting).Subscribe();
 
             Assert.Equal(1, isExecuting.Count);
             Assert.False(isExecuting[0]);
@@ -1041,9 +1041,9 @@ public void IsExecutingTicksAsExecutionsProgress() =>
             new TestScheduler().With(
                 scheduler =>
                 {
-                    IObservable<Unit> execute = Observables.Unit.Delay(TimeSpan.FromSeconds(1), scheduler);
+                    var execute = Observables.Unit.Delay(TimeSpan.FromSeconds(1), scheduler);
                     ReactiveCommand<Unit, Unit> fixture = ReactiveCommand.CreateFromObservable(() => execute, outputScheduler: scheduler);
-                    fixture.IsExecuting.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<bool> isExecuting).Subscribe();
+                    fixture.IsExecuting.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var isExecuting).Subscribe();
 
                     fixture.Execute().Subscribe();
                     scheduler.AdvanceByMs(100);
@@ -1067,7 +1067,7 @@ public void ResultIsTickedThroughSpecifiedScheduler() =>
                 scheduler =>
                 {
                     ReactiveCommand<Unit, IObservable<Unit>> fixture = ReactiveCommand.Create(() => Observables.Unit, outputScheduler: scheduler);
-                    fixture.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out ReadOnlyObservableCollection<IObservable<Unit>> results).Subscribe();
+                    fixture.ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var results).Subscribe();
 
                     fixture.Execute().Subscribe();
                     Assert.Empty(results);
@@ -1082,7 +1082,7 @@ public void ResultIsTickedThroughSpecifiedScheduler() =>
         [Fact]
         public void SynchronousCommandExecuteLazily()
         {
-            int executionCount = 0;
+            var executionCount = 0;
             ReactiveCommand<Unit, Unit> fixture1 = ReactiveCommand.Create(() => { ++executionCount; }, outputScheduler: ImmediateScheduler.Instance);
             ReactiveCommand<int, Unit> fixture2 = ReactiveCommand.Create<int>(_ => { ++executionCount; }, outputScheduler: ImmediateScheduler.Instance);
             ReactiveCommand<Unit, int> fixture3 = ReactiveCommand.Create(
@@ -1099,10 +1099,10 @@ public void SynchronousCommandExecuteLazily()
                                                                 return 42;
                                                             },
                                                             outputScheduler: ImmediateScheduler.Instance);
-            IObservable<Unit> execute1 = fixture1.Execute();
-            IObservable<Unit> execute2 = fixture2.Execute();
-            IObservable<int> execute3 = fixture3.Execute();
-            IObservable<int> execute4 = fixture4.Execute();
+            var execute1 = fixture1.Execute();
+            var execute2 = fixture2.Execute();
+            var execute3 = fixture3.Execute();
+            var execute4 = fixture4.Execute();
 
             Assert.Equal(0, executionCount);
 
@@ -1130,7 +1130,7 @@ public void SynchronousCommandsFailCorrectly()
             ReactiveCommand<Unit, Unit> fixture3 = ReactiveCommand.Create(() => throw new InvalidOperationException(), outputScheduler: ImmediateScheduler.Instance);
             ReactiveCommand<int, int> fixture4 = ReactiveCommand.Create<int, int>(_ => throw new InvalidOperationException(), outputScheduler: ImmediateScheduler.Instance);
 
-            int failureCount = 0;
+            var failureCount = 0;
             Observable.Merge(fixture1.ThrownExceptions, fixture2.ThrownExceptions, fixture3.ThrownExceptions, fixture4.ThrownExceptions).Subscribe(_ => ++failureCount);
 
             fixture1.Execute().Subscribe(_ => { }, _ => { });
diff --git a/src/ReactiveUI.Tests/InteractionBinding/InteractionBinderImplementationTests.cs b/src/ReactiveUI.Tests/InteractionBinding/InteractionBinderImplementationTests.cs
index 26a6fe9153..82c3f51d3e 100644
--- a/src/ReactiveUI.Tests/InteractionBinding/InteractionBinderImplementationTests.cs
+++ b/src/ReactiveUI.Tests/InteractionBinding/InteractionBinderImplementationTests.cs
@@ -39,7 +39,7 @@ public async Task ReceiveOutputFromTaskHandler()
                         return Task.CompletedTask;
                     });
 
-            bool isDeletionConfirmed = await vm.Interaction1.Handle("123");
+            var isDeletionConfirmed = await vm.Interaction1.Handle("123");
 
             isDeletionConfirmed.Should().BeTrue();
         }
@@ -63,7 +63,7 @@ public async Task ReceiveOutputFromObservableHandler()
                     return Observable.Return(Unit.Default);
                 });
 
-            bool isDeletionConfirmed = await vm.Interaction1.Handle("123");
+            var isDeletionConfirmed = await vm.Interaction1.Handle("123");
 
             isDeletionConfirmed.Should().BeTrue();
         }
@@ -89,7 +89,7 @@ public async Task ReceiveOutputFromTaskHandlerWhenViewModelWasInitiallyNull()
 
             view.ViewModel = new InteractionBindViewModel();
 
-            bool isDeletionConfirmed = await view.ViewModel.Interaction1.Handle("123");
+            var isDeletionConfirmed = await view.ViewModel.Interaction1.Handle("123");
 
             isDeletionConfirmed.Should().BeTrue();
         }
@@ -115,7 +115,7 @@ public async Task ReceiveOutputFromObservableHandlerWhenViewModelWasInitiallyNul
 
             view.ViewModel = new InteractionBindViewModel();
 
-            bool isDeletionConfirmed = await view.ViewModel.Interaction1.Handle("123");
+            var isDeletionConfirmed = await view.ViewModel.Interaction1.Handle("123");
 
             isDeletionConfirmed.Should().BeTrue();
         }
@@ -233,7 +233,7 @@ public async Task RegisterTaskHandlerToNewlyAssignedViewModel()
 
             view.ViewModel = new InteractionBindViewModel();
 
-            bool isDeletionConfirmed = await view.ViewModel.Interaction1.Handle("123");
+            var isDeletionConfirmed = await view.ViewModel.Interaction1.Handle("123");
 
             isDeletionConfirmed.Should().BeTrue();
         }
@@ -259,7 +259,7 @@ public async Task RegisterObservableHandlerToNewlyAssignedViewModel()
 
             view.ViewModel = new InteractionBindViewModel();
 
-            bool isDeletionConfirmed = await view.ViewModel.Interaction1.Handle("123");
+            var isDeletionConfirmed = await view.ViewModel.Interaction1.Handle("123");
 
             isDeletionConfirmed.Should().BeTrue();
         }
@@ -283,7 +283,7 @@ public async Task NestedInteractionShouldReceiveOutputFromTaskHandler()
                     return Task.CompletedTask;
                 });
 
-            bool isDeletionConfirmed = await vm.InteractionViewModel.Interaction1.Handle("123");
+            var isDeletionConfirmed = await vm.InteractionViewModel.Interaction1.Handle("123");
 
             isDeletionConfirmed.Should().BeTrue();
         }
@@ -307,7 +307,7 @@ public async Task NestedInteractionShouldReceiveOutputFromObservableHandler()
                     return Observable.Return(Unit.Default);
                 });
 
-            bool isDeletionConfirmed = await vm.InteractionViewModel.Interaction1.Handle("123");
+            var isDeletionConfirmed = await vm.InteractionViewModel.Interaction1.Handle("123");
 
             isDeletionConfirmed.Should().BeTrue();
         }
@@ -384,7 +384,7 @@ public async Task RegisterTaskHandlerToNewlyAssignedNestedViewModel()
 
             vm.InteractionViewModel = new InteractionBindViewModel();
 
-            bool isDeletionConfirmed = await vm.InteractionViewModel.Interaction1.Handle("123");
+            var isDeletionConfirmed = await vm.InteractionViewModel.Interaction1.Handle("123");
 
             isDeletionConfirmed.Should().BeTrue();
         }
@@ -413,7 +413,7 @@ public async Task RegisterObservableHandlerToNewlyAssignedNestedViewModel()
 
             vm.InteractionViewModel = new InteractionBindViewModel();
 
-            bool isDeletionConfirmed = await vm.InteractionViewModel.Interaction1.Handle("123");
+            var isDeletionConfirmed = await vm.InteractionViewModel.Interaction1.Handle("123");
 
             isDeletionConfirmed.Should().BeTrue();
         }
diff --git a/src/ReactiveUI.Tests/ObservableAsPropertyHelper/ObservableAsPropertyHelperTest.cs b/src/ReactiveUI.Tests/ObservableAsPropertyHelper/ObservableAsPropertyHelperTest.cs
index 5a2c79d1e9..b000fbbc15 100644
--- a/src/ReactiveUI.Tests/ObservableAsPropertyHelper/ObservableAsPropertyHelperTest.cs
+++ b/src/ReactiveUI.Tests/ObservableAsPropertyHelper/ObservableAsPropertyHelperTest.cs
@@ -275,7 +275,7 @@ public void OAPHDeferSubscriptionWithInitialValueEmitInitialValueWhenSubscribed(
         public void OAPHDeferSubscriptionWithInitialFuncValueEmitInitialValueWhenSubscribed()
         {
             var observable = Observable.Empty<int>();
-            bool wasAccessed = false;
+            var wasAccessed = false;
             Func<int> getInitialValue = () =>
             {
                 wasAccessed = true;
diff --git a/src/ReactiveUI.Tests/ObservedChanged/ObservedChangedMixinTest.cs b/src/ReactiveUI.Tests/ObservedChanged/ObservedChangedMixinTest.cs
index 48da5d6e23..e8f6d1a995 100644
--- a/src/ReactiveUI.Tests/ObservedChanged/ObservedChangedMixinTest.cs
+++ b/src/ReactiveUI.Tests/ObservedChanged/ObservedChangedMixinTest.cs
@@ -151,15 +151,15 @@ public void BindToIsNotFooledByIntermediateObjectSwitching() =>
 
                 input.OnNext("Foo");
                 scheduler.Start();
-                Assert.Equal("Foo", fixture.Child.IsNotNullString);
+                Assert.Equal("Foo", fixture.Child!.IsNotNullString);
 
                 fixture.Child = new TestFixture();
                 scheduler.Start();
-                Assert.Equal("Foo", fixture.Child.IsNotNullString);
+                Assert.Equal("Foo", fixture.Child!.IsNotNullString);
 
                 input.OnNext("Bar");
                 scheduler.Start();
-                Assert.Equal("Bar", fixture.Child.IsNotNullString);
+                Assert.Equal("Bar", fixture.Child!.IsNotNullString);
             });
 
         /// <summary>
diff --git a/src/ReactiveUI.Tests/Platforms/windows-xaml/WhenAnyThroughDependencyObjectTests.cs b/src/ReactiveUI.Tests/Platforms/windows-xaml/WhenAnyThroughDependencyObjectTests.cs
index 71a47fa61d..39e05917bf 100644
--- a/src/ReactiveUI.Tests/Platforms/windows-xaml/WhenAnyThroughDependencyObjectTests.cs
+++ b/src/ReactiveUI.Tests/Platforms/windows-xaml/WhenAnyThroughDependencyObjectTests.cs
@@ -35,7 +35,7 @@ public void WhenAnyThroughAViewShouldntGiveNullValues()
                 },
             };
 
-            var fixture = new HostTestView();
+            HostTestView? fixture = new();
 
             var output = new List<string?>();
 
diff --git a/src/ReactiveUI.Tests/Platforms/winforms/API/ApiApprovalTests.Winforms.net472.approved.txt b/src/ReactiveUI.Tests/Platforms/winforms/API/ApiApprovalTests.Winforms.net472.approved.txt
index 45976e7fb2..8379dd8768 100644
--- a/src/ReactiveUI.Tests/Platforms/winforms/API/ApiApprovalTests.Winforms.net472.approved.txt
+++ b/src/ReactiveUI.Tests/Platforms/winforms/API/ApiApprovalTests.Winforms.net472.approved.txt
@@ -23,7 +23,7 @@ namespace ReactiveUI.Winforms
     public class PanelSetMethodBindingConverter : ReactiveUI.ISetMethodBindingConverter, Splat.IEnableLogger
     {
         public PanelSetMethodBindingConverter() { }
-        public int GetAffinityForObjects(System.Type fromType, System.Type toType) { }
+        public int GetAffinityForObjects(System.Type? fromType, System.Type? toType) { }
         public object PerformSet(object? toTarget, object? newValue, object?[]? arguments) { }
     }
     public class PlatformOperations : ReactiveUI.IPlatformOperations
@@ -68,7 +68,7 @@ namespace ReactiveUI.Winforms
     public class TableContentSetMethodBindingConverter : ReactiveUI.ISetMethodBindingConverter, Splat.IEnableLogger
     {
         public TableContentSetMethodBindingConverter() { }
-        public int GetAffinityForObjects(System.Type fromType, System.Type toType) { }
+        public int GetAffinityForObjects(System.Type? fromType, System.Type? toType) { }
         public object PerformSet(object? toTarget, object? newValue, object?[]? arguments) { }
     }
     [System.ComponentModel.DefaultProperty("ViewModel")]
diff --git a/src/ReactiveUI.Tests/Platforms/winforms/API/ApiApprovalTests.Winforms.net5.0.approved.txt b/src/ReactiveUI.Tests/Platforms/winforms/API/ApiApprovalTests.Winforms.net5.0.approved.txt
index 3b7a5874ca..faef9a0256 100644
--- a/src/ReactiveUI.Tests/Platforms/winforms/API/ApiApprovalTests.Winforms.net5.0.approved.txt
+++ b/src/ReactiveUI.Tests/Platforms/winforms/API/ApiApprovalTests.Winforms.net5.0.approved.txt
@@ -25,7 +25,7 @@ namespace ReactiveUI.Winforms
     public class PanelSetMethodBindingConverter : ReactiveUI.ISetMethodBindingConverter, Splat.IEnableLogger
     {
         public PanelSetMethodBindingConverter() { }
-        public int GetAffinityForObjects(System.Type fromType, System.Type toType) { }
+        public int GetAffinityForObjects(System.Type? fromType, System.Type? toType) { }
         public object PerformSet(object? toTarget, object? newValue, object?[]? arguments) { }
     }
     public class PlatformOperations : ReactiveUI.IPlatformOperations
@@ -70,7 +70,7 @@ namespace ReactiveUI.Winforms
     public class TableContentSetMethodBindingConverter : ReactiveUI.ISetMethodBindingConverter, Splat.IEnableLogger
     {
         public TableContentSetMethodBindingConverter() { }
-        public int GetAffinityForObjects(System.Type fromType, System.Type toType) { }
+        public int GetAffinityForObjects(System.Type? fromType, System.Type? toType) { }
         public object PerformSet(object? toTarget, object? newValue, object?[]? arguments) { }
     }
     [System.ComponentModel.DefaultProperty("ViewModel")]
diff --git a/src/ReactiveUI.Tests/Platforms/winforms/API/ApiApprovalTests.Winforms.netcoreapp3.1.approved.txt b/src/ReactiveUI.Tests/Platforms/winforms/API/ApiApprovalTests.Winforms.netcoreapp3.1.approved.txt
index db75d8a4e5..5448194b7e 100644
--- a/src/ReactiveUI.Tests/Platforms/winforms/API/ApiApprovalTests.Winforms.netcoreapp3.1.approved.txt
+++ b/src/ReactiveUI.Tests/Platforms/winforms/API/ApiApprovalTests.Winforms.netcoreapp3.1.approved.txt
@@ -23,7 +23,7 @@ namespace ReactiveUI.Winforms
     public class PanelSetMethodBindingConverter : ReactiveUI.ISetMethodBindingConverter, Splat.IEnableLogger
     {
         public PanelSetMethodBindingConverter() { }
-        public int GetAffinityForObjects(System.Type fromType, System.Type toType) { }
+        public int GetAffinityForObjects(System.Type? fromType, System.Type? toType) { }
         public object PerformSet(object? toTarget, object? newValue, object?[]? arguments) { }
     }
     public class PlatformOperations : ReactiveUI.IPlatformOperations
@@ -68,7 +68,7 @@ namespace ReactiveUI.Winforms
     public class TableContentSetMethodBindingConverter : ReactiveUI.ISetMethodBindingConverter, Splat.IEnableLogger
     {
         public TableContentSetMethodBindingConverter() { }
-        public int GetAffinityForObjects(System.Type fromType, System.Type toType) { }
+        public int GetAffinityForObjects(System.Type? fromType, System.Type? toType) { }
         public object PerformSet(object? toTarget, object? newValue, object?[]? arguments) { }
     }
     [System.ComponentModel.DefaultProperty("ViewModel")]
diff --git a/src/ReactiveUI.Tests/ReactiveObject/ReactiveObjectTests.cs b/src/ReactiveUI.Tests/ReactiveObject/ReactiveObjectTests.cs
index 379888c03a..938c565adf 100644
--- a/src/ReactiveUI.Tests/ReactiveObject/ReactiveObjectTests.cs
+++ b/src/ReactiveUI.Tests/ReactiveObject/ReactiveObjectTests.cs
@@ -205,7 +205,7 @@ public void ReactiveObjectShouldntSerializeAnythingExtra()
                 IsNotNullString = "Foo",
                 IsOnlyOneWord = "Baz"
             };
-            string? json = JSONHelper.Serialize(fixture);
+            var json = JSONHelper.Serialize(fixture);
 
             if (json is null)
             {
diff --git a/src/ReactiveUI.Tests/Resolvers/DependencyResolverTests.cs b/src/ReactiveUI.Tests/Resolvers/DependencyResolverTests.cs
index 0faefdbf54..f73771caa1 100644
--- a/src/ReactiveUI.Tests/Resolvers/DependencyResolverTests.cs
+++ b/src/ReactiveUI.Tests/Resolvers/DependencyResolverTests.cs
@@ -56,9 +56,9 @@ public void AllDefaultServicesShouldBeRegistered()
             {
                 foreach (var shouldRegistered in GetServicesThatShouldBeRegistered(PlatformRegistrationManager.DefaultRegistrationNamespaces))
                 {
-                    IEnumerable<object> resolvedServices = resolver.GetServices(shouldRegistered.Key);
+                    var resolvedServices = resolver.GetServices(shouldRegistered.Key);
                     Assert.Equal(shouldRegistered.Value.Count, resolvedServices.Count());
-                    foreach (Type implementationType in shouldRegistered.Value)
+                    foreach (var implementationType in shouldRegistered.Value)
                     {
                         resolvedServices
                             .Any(rs => rs.GetType() == implementationType)
@@ -83,9 +83,9 @@ public void AllDefaultServicesShouldBeRegisteredPerRegistrationNamespace(IEnumer
 
                 foreach (var shouldRegistered in registeredService)
                 {
-                    IEnumerable<object> resolvedServices = resolver.GetServices(shouldRegistered.Key);
+                    var resolvedServices = resolver.GetServices(shouldRegistered.Key);
 
-                    foreach (Type implementationType in shouldRegistered.Value)
+                    foreach (var implementationType in shouldRegistered.Value)
                     {
                         resolvedServices
                             .Any(rs => rs.GetType() == implementationType)
@@ -109,7 +109,7 @@ public void RegisteredNamespacesShouldBeRegistered(IEnumerable<RegistrationNames
 
                 foreach (var shouldRegistered in GetServicesThatShouldBeRegistered(namespaces))
                 {
-                    IEnumerable<object> resolvedServices = resolver.GetServices(shouldRegistered.Key);
+                    var resolvedServices = resolver.GetServices(shouldRegistered.Key);
 
                     resolvedServices
                         .Select(x => x.GetType()?.AssemblyQualifiedName ?? string.Empty)
diff --git a/src/ReactiveUI.Tests/Resolvers/PocoObservableForPropertyTests.cs b/src/ReactiveUI.Tests/Resolvers/PocoObservableForPropertyTests.cs
index 839cd794e6..312f6cc095 100644
--- a/src/ReactiveUI.Tests/Resolvers/PocoObservableForPropertyTests.cs
+++ b/src/ReactiveUI.Tests/Resolvers/PocoObservableForPropertyTests.cs
@@ -41,7 +41,7 @@ public void NotificationPocoErrorOnBind()
             }
 
             // Run test twice and verify that POCO message is logged only once.
-            for (int i = 0; i < 2; i++)
+            for (var i = 0; i < 2; i++)
             {
                 using (var testLoggerRegistration = new TestLoggerRegistration(_testLoggerForNotificationPocoErrorOnBind))
                 {
diff --git a/src/ReactiveUI.Tests/Utilities/ApiApprovalBase.cs b/src/ReactiveUI.Tests/Utilities/ApiApprovalBase.cs
index 256163244c..08ae4ff50e 100644
--- a/src/ReactiveUI.Tests/Utilities/ApiApprovalBase.cs
+++ b/src/ReactiveUI.Tests/Utilities/ApiApprovalBase.cs
@@ -41,7 +41,7 @@ protected static void CheckApproval(Assembly assembly, [CallerMemberName]string?
             var approvedFileName = Path.Combine(sourceDirectory, $"ApiApprovalTests.{memberName}.{targetFrameworkName}.approved.txt");
             var receivedFileName = Path.Combine(sourceDirectory, $"ApiApprovalTests.{memberName}.{targetFrameworkName}.received.txt");
 
-            string approvedPublicApi = string.Empty;
+            var approvedPublicApi = string.Empty;
 
             if (File.Exists(approvedFileName))
             {
@@ -76,7 +76,7 @@ protected static void CheckApproval(Assembly assembly, [CallerMemberName]string?
                     process.StartInfo.FileName = "diff";
 #endif
                     process.Start();
-                    string output = process.StandardOutput.ReadToEnd();
+                    var output = process.StandardOutput.ReadToEnd();
                     process.WaitForExit();
 
                     throw new Exception("Invalid API configuration: " + Environment.NewLine + output);
diff --git a/src/ReactiveUI.Tests/WhenAny/ReactiveNotifyPropertyChangedMixinTest.cs b/src/ReactiveUI.Tests/WhenAny/ReactiveNotifyPropertyChangedMixinTest.cs
index 3723b2c6c1..bf412e1af5 100644
--- a/src/ReactiveUI.Tests/WhenAny/ReactiveNotifyPropertyChangedMixinTest.cs
+++ b/src/ReactiveUI.Tests/WhenAny/ReactiveNotifyPropertyChangedMixinTest.cs
@@ -35,7 +35,7 @@ public class ReactiveNotifyPropertyChangedMixinTest
         [Fact]
         public void AnyChangeInExpressionListTriggersUpdate()
         {
-            var obj = new ObjChain1();
+            ObjChain1? obj = new();
             bool obsUpdated;
 
             obj.ObservableForProperty(x => x.Model.Model.Model.SomeOtherParam).Subscribe(_ => obsUpdated = true);
@@ -101,12 +101,7 @@ public void MultiPropertyExpressionsShouldBeProperlyResolved()
                 {
                     var propertyName = y.GetMemberInfo()?.Name;
 
-                    if (propertyName is null)
-                    {
-                        throw new InvalidOperationException("propertyName should not be null.");
-                    }
-
-                    return propertyName;
+                    return propertyName ?? throw new InvalidOperationException("propertyName should not be null.");
                 }));
             }
 
@@ -120,7 +115,7 @@ public void MultiPropertyExpressionsShouldBeProperlyResolved()
         public void OFPChangingTheHostPropertyShouldFireAChildChangeNotificationOnlyIfThePreviousChildIsDifferent() =>
             new TestScheduler().With(scheduler =>
             {
-                var fixture = new HostTestFixture
+                HostTestFixture? fixture = new()
                               {
                                   Child = new TestFixture()
                               };
@@ -180,7 +175,7 @@ public void OFPNamedPropertyTest() =>
         public void OFPNamedPropertyTestBeforeChange() =>
             new TestScheduler().With(scheduler =>
             {
-                var fixture = new TestFixture
+                TestFixture? fixture = new()
                               {
                                   IsOnlyOneWord = "Pre"
                               };
@@ -209,7 +204,7 @@ public void OFPNamedPropertyTestBeforeChange() =>
         public void OFPNamedPropertyTestNoSkipInitial() =>
             new TestScheduler().With(scheduler =>
             {
-                var fixture = new TestFixture
+                TestFixture? fixture = new()
                               {
                                   IsOnlyOneWord = "Pre"
                               };
@@ -234,7 +229,7 @@ public void OFPNamedPropertyTestNoSkipInitial() =>
         public void OFPNamedPropertyTestRepeats() =>
             new TestScheduler().With(scheduler =>
             {
-                var fixture = new TestFixture();
+                TestFixture? fixture = new();
                 fixture.ObservableForProperty(x => x.IsOnlyOneWord)
                        .ToObservableChangeSet(ImmediateScheduler.Instance)
                        .Bind(out var changes)
@@ -265,7 +260,7 @@ public void OFPNamedPropertyTestRepeats() =>
         public void OFPReplacingTheHostShouldResubscribeTheObservable() =>
             new TestScheduler().With(scheduler =>
             {
-                var fixture = new HostTestFixture
+                HostTestFixture? fixture = new()
                               {
                                   Child = new TestFixture()
                               };
@@ -310,7 +305,7 @@ public void OFPReplacingTheHostShouldResubscribeTheObservable() =>
         public void OFPReplacingTheHostWithNullThenSettingItBackShouldResubscribeTheObservable() =>
             new TestScheduler().With(scheduler =>
             {
-                var fixture = new HostTestFixture
+                HostTestFixture? fixture = new()
                               {
                                   Child = new TestFixture()
                               };
@@ -350,7 +345,7 @@ public void OFPReplacingTheHostWithNullThenSettingItBackShouldResubscribeTheObse
         public void OFPShouldWorkWithINPCObjectsToo() =>
             new TestScheduler().With(scheduler =>
             {
-                var fixture = new NonReactiveINPCObject
+                NonReactiveINPCObject? fixture = new()
                               {
                                   InpcProperty = null!
                               };
@@ -376,7 +371,7 @@ public void OFPShouldWorkWithINPCObjectsToo() =>
         public void OFPSimpleChildPropertyTest() =>
             new TestScheduler().With(scheduler =>
             {
-                var fixture = new HostTestFixture
+                HostTestFixture? fixture = new()
                               {
                                   Child = new TestFixture()
                               };
@@ -410,7 +405,7 @@ public void OFPSimpleChildPropertyTest() =>
         public void OFPSimplePropertyTest() =>
             new TestScheduler().With(scheduler =>
             {
-                var fixture = new TestFixture();
+                TestFixture? fixture = new();
                 fixture.ObservableForProperty(x => x.IsOnlyOneWord)
                        .ToObservableChangeSet(ImmediateScheduler.Instance)
                        .Bind(out var changes)
@@ -440,7 +435,7 @@ public void OFPSimplePropertyTest() =>
         [Fact]
         public void SubscriptionToWhenAnyShouldReturnCurrentValue()
         {
-            var obj = new HostTestFixture();
+            HostTestFixture? obj = new();
             var observedValue = 1;
             obj.WhenAnyValue(x => x.SomeOtherParam).Subscribe(x => observedValue = x);
 
@@ -455,7 +450,7 @@ public void WhenAnyShouldRunInContext()
             var tid = Thread.CurrentThread.ManagedThreadId;
 
             TaskPoolScheduler.Default.With(
-                                           scheduler =>
+                                           _ =>
                                            {
                                                var whenAnyTid = 0;
                                                var fixture = new TestFixture
@@ -465,7 +460,7 @@ public void WhenAnyShouldRunInContext()
                                                    PocoProperty = "Bamf"
                                                };
 
-                                               fixture.WhenAnyValue(x => x.IsNotNullString).Subscribe(x => { whenAnyTid = Thread.CurrentThread.ManagedThreadId; });
+                                               fixture.WhenAnyValue(x => x.IsNotNullString).Subscribe(__ => whenAnyTid = Thread.CurrentThread.ManagedThreadId);
 
                                                var timeout = 10;
                                                fixture.IsNotNullString = "Bar";
@@ -488,28 +483,28 @@ public void WhenAnyShouldWorkEvenWithNormalProperties()
                 PocoProperty = "Bamf"
             };
 
-            var output = new List<IObservedChange<TestFixture, string?>>();
+            var output = new List<IObservedChange<TestFixture, string?>?>();
             fixture.WhenAny(x => x.PocoProperty, x => x).Subscribe(output.Add);
             var output2 = new List<string?>();
             fixture.WhenAnyValue(x => x.PocoProperty).Subscribe(output2.Add);
-            var output3 = new List<IObservedChange<TestFixture, int?>>();
+            var output3 = new List<IObservedChange<TestFixture, int?>?>();
             fixture.WhenAny(x => x.NullableInt, x => x).Subscribe(output3.Add);
 
             var output4 = new List<int?>();
             fixture.WhenAnyValue(x => x.NullableInt).Subscribe(output4.Add);
 
             Assert.Equal(1, output.Count);
-            Assert.Equal(fixture, output[0].Sender);
-            Assert.Equal("PocoProperty", output[0].GetPropertyName());
-            Assert.Equal("Bamf", output[0].Value);
+            Assert.Equal(fixture, output[0]!.Sender);
+            Assert.Equal("PocoProperty", output[0]!.GetPropertyName());
+            Assert.Equal("Bamf", output[0]!.Value);
 
             Assert.Equal(1, output2.Count);
             Assert.Equal("Bamf", output2[0]);
 
             Assert.Equal(1, output3.Count);
-            Assert.Equal(fixture, output3[0].Sender);
-            Assert.Equal("NullableInt", output3[0].GetPropertyName());
-            Assert.Equal(null, output3[0].Value);
+            Assert.Equal(fixture, output3[0]!.Sender);
+            Assert.Equal("NullableInt", output3[0]!.GetPropertyName());
+            Assert.Equal(null, output3[0]!.Value);
 
             Assert.Equal(1, output4.Count);
             Assert.Equal(null, output4[0]);
@@ -584,7 +579,7 @@ public void WhenAnySmokeTest() =>
             new TestScheduler().With(
                 scheduler =>
                 {
-                    var fixture = new HostTestFixture
+                    HostTestFixture? fixture = new()
                                   {
                                       Child = new TestFixture()
                                   };
@@ -603,7 +598,7 @@ public void WhenAnySmokeTest() =>
                                       }).Subscribe(
                         x =>
                         {
-                            output1.Add(x.sop);
+                            output1.Add(x!.sop);
                             output2.Add(x.nns!);
                         });
 
@@ -660,7 +655,7 @@ public void WhenAnyValueSmokeTest() =>
             new TestScheduler().With(
                 scheduler =>
                 {
-                    var fixture = new HostTestFixture
+                    HostTestFixture? fixture = new()
                                   {
                                       Child = new TestFixture()
                                   };
@@ -679,7 +674,7 @@ public void WhenAnyValueSmokeTest() =>
                                       }).Subscribe(
                         x =>
                         {
-                            output1.Add(x.sop);
+                            output1.Add(x!.sop);
                             output2.Add(x.nns!);
                         });
 
@@ -764,7 +759,7 @@ public void WhenAnyValueUnsupportedExpressionType_Constant()
         {
             var fixture = new TestFixture();
             var exception = Assert.Throws<NotSupportedException>(
-                () => fixture.WhenAnyValue(x => Dummy).Subscribe());
+                () => fixture.WhenAnyValue(_ => Dummy).Subscribe());
 
             Assert.Equal("Unsupported expression of type 'Constant'. Did you miss the member access prefix in the expression?", exception.Message);
         }
diff --git a/src/ReactiveUI.Tests/WhenAny/WhenAnyObservableTests.cs b/src/ReactiveUI.Tests/WhenAny/WhenAnyObservableTests.cs
index 7d34626ce0..3eaca76138 100644
--- a/src/ReactiveUI.Tests/WhenAny/WhenAnyObservableTests.cs
+++ b/src/ReactiveUI.Tests/WhenAny/WhenAnyObservableTests.cs
@@ -27,11 +27,10 @@ public class WhenAnyObservableTests
         [Fact]
         public void NullObservablesDoNotCauseExceptions()
         {
-            var fixture = new TestWhenAnyObsViewModel();
+            TestWhenAnyObsViewModel? fixture = new();
             fixture.Command1 = null;
 
             // these are the overloads of WhenAnyObservable that perform a Merge
-#pragma warning disable CS8603 // Possible null reference return.
             fixture.WhenAnyObservable(x => x.Command1).Subscribe();
             fixture.WhenAnyObservable(x => x.Command1, x => x.Command1).Subscribe();
             fixture.WhenAnyObservable(x => x.Command1, x => x.Command1, x => x.Command1).Subscribe();
@@ -45,6 +44,7 @@ public void NullObservablesDoNotCauseExceptions()
             fixture.WhenAnyObservable(x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1).Subscribe();
 
             // these are the overloads of WhenAnyObservable that perform a CombineLatest
+#pragma warning disable RCS1163 // Unused parameter.
             fixture.WhenAnyObservable(x => x.Command1, x => x.Command1, (zero, one) => Unit.Default).Subscribe();
             fixture.WhenAnyObservable(x => x.Command1, x => x.Command1, x => x.Command1, (zero, one, two) => Unit.Default).Subscribe();
             fixture.WhenAnyObservable(x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, (zero, one, two, three) => Unit.Default).Subscribe();
@@ -55,7 +55,7 @@ public void NullObservablesDoNotCauseExceptions()
             fixture.WhenAnyObservable(x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, (zero, one, two, three, four, five, six, seven, eight) => Unit.Default).Subscribe();
             fixture.WhenAnyObservable(x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, (zero, one, two, three, four, five, six, seven, eight, nine) => Unit.Default).Subscribe();
             fixture.WhenAnyObservable(x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, x => x.Command1, (zero, one, two, three, four, five, six, seven, eight, nine, ten) => Unit.Default).Subscribe();
-#pragma warning restore CS8603 // Possible null reference return.
+#pragma warning restore RCS1163 // Unused parameter.
         }
 
         /// <summary>
@@ -65,13 +65,10 @@ public void NullObservablesDoNotCauseExceptions()
         [Fact]
         public async Task WhenAnyObservableSmokeTestCombining()
         {
-            var fixture = new TestWhenAnyObsViewModel();
+            TestWhenAnyObsViewModel? fixture = new();
 
-            var list = new List<string>();
-#pragma warning disable CS8603 // Possible null reference return.
+            var list = new List<string?>();
             fixture.WhenAnyObservable(x => x.Command3, x => x.Command1, (s, i) => s + " : " + i).ObserveOn(ImmediateScheduler.Instance).Subscribe(list.Add);
-#pragma warning restore CS8603 // Possible null reference return.
-
             Assert.Equal(0, list.Count);
 
             await fixture.Command1!.Execute(1);
@@ -101,13 +98,10 @@ public async Task WhenAnyObservableSmokeTestCombining()
         [Fact]
         public async Task WhenAnyObservableSmokeTestMerging()
         {
-            var fixture = new TestWhenAnyObsViewModel();
+            TestWhenAnyObsViewModel fixture = new();
 
             var list = new List<int>();
-#pragma warning disable CS8603 // Possible null reference return.
             fixture.WhenAnyObservable(x => x.Command1, x => x.Command2).ObserveOn(ImmediateScheduler.Instance).Subscribe(list.Add);
-#pragma warning restore CS8603 // Possible null reference return.
-
             Assert.Equal(0, list.Count);
 
             await fixture.Command1!.Execute(1);
@@ -135,11 +129,8 @@ public async Task WhenAnyObservableSmokeTestMerging()
         [Fact]
         public void WhenAnyObservableWithNullObjectShouldUpdateWhenObjectIsntNullAnymore()
         {
-            var fixture = new TestWhenAnyObsViewModel();
-#pragma warning disable CS8603 // Possible null reference return.
-            fixture.WhenAnyObservable(x => x.Changes).Bind(out var output).ObserveOn(ImmediateScheduler.Instance).Subscribe();
-#pragma warning restore CS8603  // Possible null reference return.
-
+            TestWhenAnyObsViewModel? fixture = new();
+            fixture!.WhenAnyObservable(x => x.Changes)!.Bind(out var output).ObserveOn(ImmediateScheduler.Instance).Subscribe();
             Assert.Equal(0, output.Count);
 
             fixture.MyListOfInts = new ObservableCollectionExtended<int>();
diff --git a/src/ReactiveUI.Winforms/ActivationForViewFetcher.cs b/src/ReactiveUI.Winforms/ActivationForViewFetcher.cs
index 360b83c8d0..cccb4aabc1 100644
--- a/src/ReactiveUI.Winforms/ActivationForViewFetcher.cs
+++ b/src/ReactiveUI.Winforms/ActivationForViewFetcher.cs
@@ -93,7 +93,7 @@ public IObservable<bool> GetActivationForView(IActivatableView view)
 
         private static bool GetIsDesignMode(Control control)
         {
-            bool isDesignMode = LicenseManager.UsageMode == LicenseUsageMode.Designtime || control.Site?.DesignMode == true || control.Parent?.Site?.DesignMode == true;
+            var isDesignMode = LicenseManager.UsageMode == LicenseUsageMode.Designtime || control.Site?.DesignMode == true || control.Parent?.Site?.DesignMode == true;
 
             return isDesignMode;
         }
diff --git a/src/ReactiveUI.Winforms/CreatesWinformsCommandBinding.cs b/src/ReactiveUI.Winforms/CreatesWinformsCommandBinding.cs
index d403d3cdbb..d71a7d8b8a 100644
--- a/src/ReactiveUI.Winforms/CreatesWinformsCommandBinding.cs
+++ b/src/ReactiveUI.Winforms/CreatesWinformsCommandBinding.cs
@@ -30,7 +30,7 @@ public class CreatesWinformsCommandBinding : ICreatesCommandBinding
         /// <inheritdoc/>
         public int GetAffinityForObject(Type type, bool hasEventTarget)
         {
-            bool isWinformControl = typeof(Control).IsAssignableFrom(type);
+            var isWinformControl = typeof(Control).IsAssignableFrom(type);
 
             if (isWinformControl)
             {
@@ -91,7 +91,7 @@ public IDisposable BindCommandToObject<TEventArgs>(ICommand command, object targ
             var ret = new CompositeDisposable();
 
             object? latestParameter = null;
-            Type targetType = target.GetType();
+            var targetType = target.GetType();
 
             ret.Add(commandParameter.Subscribe(x => latestParameter = x));
 
diff --git a/src/ReactiveUI.Winforms/ObservableCollectionChangedToListChangedTransformer.cs b/src/ReactiveUI.Winforms/ObservableCollectionChangedToListChangedTransformer.cs
index f2ba182727..f988ccc53c 100644
--- a/src/ReactiveUI.Winforms/ObservableCollectionChangedToListChangedTransformer.cs
+++ b/src/ReactiveUI.Winforms/ObservableCollectionChangedToListChangedTransformer.cs
@@ -31,7 +31,7 @@ internal static IEnumerable<ListChangedEventArgs> AsListChangedEventArgs(this No
 
                 case NotifyCollectionChangedAction.Remove when ea.OldItems is not null:
                 {
-                    foreach (int index in Enumerable.Range(ea.OldStartingIndex, ea.OldItems.Count))
+                    foreach (var index in Enumerable.Range(ea.OldStartingIndex, ea.OldItems.Count))
                     {
                         yield return new ListChangedEventArgs(ListChangedType.ItemDeleted, index);
                     }
@@ -41,7 +41,7 @@ internal static IEnumerable<ListChangedEventArgs> AsListChangedEventArgs(this No
 
                 case NotifyCollectionChangedAction.Add when ea.NewItems is not null:
                 {
-                    foreach (int index in Enumerable.Range(ea.NewStartingIndex, ea.NewItems.Count))
+                    foreach (var index in Enumerable.Range(ea.NewStartingIndex, ea.NewItems.Count))
                     {
                         yield return new ListChangedEventArgs(ListChangedType.ItemAdded, index);
                     }
diff --git a/src/ReactiveUI.Winforms/PanelSetMethodBindingConverter.cs b/src/ReactiveUI.Winforms/PanelSetMethodBindingConverter.cs
index 6809807781..f0f4e270a1 100644
--- a/src/ReactiveUI.Winforms/PanelSetMethodBindingConverter.cs
+++ b/src/ReactiveUI.Winforms/PanelSetMethodBindingConverter.cs
@@ -16,14 +16,16 @@ namespace ReactiveUI.Winforms
     public class PanelSetMethodBindingConverter : ISetMethodBindingConverter
     {
         /// <inheritdoc />
-        public int GetAffinityForObjects(Type fromType, Type toType)
+        public int GetAffinityForObjects(Type? fromType, Type? toType)
         {
             if (toType != typeof(Control.ControlCollection))
             {
                 return 0;
             }
 
-            if (fromType?.GetInterfaces().Any(x => x.IsGenericType && x.GetGenericTypeDefinition() == typeof(IEnumerable<>) && x.GetGenericArguments().First().IsSubclassOf(typeof(Control))) ?? false)
+#pragma warning disable IDE0046 // Convert to conditional expression
+            if (fromType?.GetInterfaces().Any(x => x.IsGenericType && x.GetGenericTypeDefinition() == typeof(IEnumerable<>) && x.GetGenericArguments()[0].IsSubclassOf(typeof(Control))) ?? false)
+#pragma warning restore IDE0046 // Convert to conditional expression
             {
                 return 10;
             }
@@ -39,7 +41,7 @@ public object PerformSet(object? toTarget, object? newValue, object?[]? argument
                 throw new ArgumentNullException(nameof(toTarget));
             }
 
-            if (!(newValue is IEnumerable<Control> newValueEnumerable))
+            if (newValue is not IEnumerable<Control> newValueEnumerable)
             {
                 throw new ArgumentException($"newValue must be {nameof(newValue)}", nameof(newValue));
             }
diff --git a/src/ReactiveUI.Winforms/RoutedViewHost.cs b/src/ReactiveUI.Winforms/RoutedViewHost.cs
index d49a6ba2c4..f8f3d0a32e 100644
--- a/src/ReactiveUI.Winforms/RoutedViewHost.cs
+++ b/src/ReactiveUI.Winforms/RoutedViewHost.cs
@@ -71,7 +71,7 @@ public RoutedControlHost()
                         return;
                     }
 
-                    IViewLocator viewLocator = ViewLocator ?? ReactiveUI.ViewLocator.Current;
+                    var viewLocator = ViewLocator ?? ReactiveUI.ViewLocator.Current;
                     var view = viewLocator.ResolveView(x.ViewModel, x.Contract);
                     if (view is not null)
                     {
diff --git a/src/ReactiveUI.Winforms/TableContentSetMethodBindingConverter.cs b/src/ReactiveUI.Winforms/TableContentSetMethodBindingConverter.cs
index 7789f8fb50..a23652d03f 100644
--- a/src/ReactiveUI.Winforms/TableContentSetMethodBindingConverter.cs
+++ b/src/ReactiveUI.Winforms/TableContentSetMethodBindingConverter.cs
@@ -16,23 +16,14 @@ namespace ReactiveUI.Winforms
     public class TableContentSetMethodBindingConverter : ISetMethodBindingConverter
     {
         /// <inheritdoc />
-        public int GetAffinityForObjects(Type fromType, Type toType)
-        {
-            if (toType != typeof(TableLayoutControlCollection))
-            {
-                return 0;
-            }
-
-            if (fromType?.GetInterfaces().Any(x => x.IsGenericType && x.GetGenericTypeDefinition() == typeof(IEnumerable<>) && x.GetGenericArguments().First().IsSubclassOf(typeof(Control))) ?? false)
-            {
-                return 15;
-            }
-
-            return 0;
-        }
+        public int GetAffinityForObjects(Type? fromType, Type? toType) =>
+            toType != typeof(TableLayoutControlCollection)
+                ? 0
+                : fromType?.GetInterfaces().Any(x => x.IsGenericType && x.GetGenericTypeDefinition() == typeof(IEnumerable<>) && x.GetGenericArguments()[0].IsSubclassOf(typeof(Control))) ?? false
+                ? 15
+                : 0;
 
         /// <inheritdoc />
-        [System.Diagnostics.CodeAnalysis.SuppressMessage("StyleCop.CSharp.SpacingRules", "SA1011:Closing square brackets should be spaced correctly", Justification = "Valid syntax.")]
         public object PerformSet(object? toTarget, object? newValue, object?[]? arguments)
         {
             if (toTarget is null)
@@ -40,12 +31,12 @@ public object PerformSet(object? toTarget, object? newValue, object?[]? argument
                 throw new ArgumentNullException(nameof(toTarget));
             }
 
-            if (!(toTarget is TableLayoutControlCollection targetCollection))
+            if (toTarget is not TableLayoutControlCollection targetCollection)
             {
                 throw new ArgumentException($"{nameof(toTarget)} must be of type {nameof(TableLayoutControlCollection)}", nameof(toTarget));
             }
 
-            if (!(newValue is IEnumerable<Control> newValueEnumerable))
+            if (newValue is not IEnumerable<Control> newValueEnumerable)
             {
                 throw new ArgumentException($"newValue must be {nameof(newValue)}", nameof(newValue));
             }
diff --git a/src/ReactiveUI.Winforms/ViewModelViewHost.cs b/src/ReactiveUI.Winforms/ViewModelViewHost.cs
index eaee85ac60..30b3dd1f9e 100644
--- a/src/ReactiveUI.Winforms/ViewModelViewHost.cs
+++ b/src/ReactiveUI.Winforms/ViewModelViewHost.cs
@@ -217,8 +217,8 @@ private IEnumerable<IDisposable> SetupBindings()
                         }
                     }
 
-                    IViewLocator viewLocator = ViewLocator ?? ReactiveUI.ViewLocator.Current;
-                    IViewFor? view = viewLocator.ResolveView(x.ViewModel, x.Contract);
+                    var viewLocator = ViewLocator ?? ReactiveUI.ViewLocator.Current;
+                    var view = viewLocator.ResolveView(x.ViewModel, x.Contract);
                     if (view != null)
                     {
                         view.ViewModel = x.ViewModel;
diff --git a/src/ReactiveUI.Winforms/WinformsCreatesObservableForProperty.cs b/src/ReactiveUI.Winforms/WinformsCreatesObservableForProperty.cs
index e178812b69..18a59eabde 100644
--- a/src/ReactiveUI.Winforms/WinformsCreatesObservableForProperty.cs
+++ b/src/ReactiveUI.Winforms/WinformsCreatesObservableForProperty.cs
@@ -30,7 +30,7 @@ public class WinformsCreatesObservableForProperty : ICreatesObservableForPropert
         /// <inheritdoc/>
         public int GetAffinityForObject(Type type, string propertyName, bool beforeChanged = false)
         {
-            bool supportsTypeBinding = typeof(Component).IsAssignableFrom(type);
+            var supportsTypeBinding = typeof(Component).IsAssignableFrom(type);
             if (!supportsTypeBinding)
             {
                 return 0;
@@ -57,7 +57,7 @@ public int GetAffinityForObject(Type type, string propertyName, bool beforeChang
 
             return Observable.Create<IObservedChange<object, object?>>(subj =>
             {
-                bool completed = false;
+                var completed = false;
                 var handler = new EventHandler((o, e) =>
                 {
                     if (completed)
diff --git a/src/ReactiveUI.Wpf/TransitioningContentControl.cs b/src/ReactiveUI.Wpf/TransitioningContentControl.cs
index 2614fe9d49..e6ddf2502f 100644
--- a/src/ReactiveUI.Wpf/TransitioningContentControl.cs
+++ b/src/ReactiveUI.Wpf/TransitioningContentControl.cs
@@ -303,7 +303,7 @@ private void QueueTransition(object newContent)
 
                 // Wire up the first transition to start the second transition when it's complete.
                 startingTransitionName = $"Transition_{Transition}{Direction}Out";
-                Storyboard transitionOut = GetTransitionStoryboardByName(startingTransitionName);
+                var transitionOut = GetTransitionStoryboardByName(startingTransitionName);
 
                 transitionOut.Completed += (_, _) => VisualStateManager.GoToState(
                     this,
diff --git a/src/ReactiveUI.XamForms/RoutedViewHost.cs b/src/ReactiveUI.XamForms/RoutedViewHost.cs
index 98a9e1f535..a8e9e6ae20 100644
--- a/src/ReactiveUI.XamForms/RoutedViewHost.cs
+++ b/src/ReactiveUI.XamForms/RoutedViewHost.cs
@@ -40,9 +40,9 @@ public RoutedViewHost()
         {
             this.WhenActivated(disposable =>
             {
-                bool currentlyPopping = false;
-                bool popToRootPending = false;
-                bool userInstigated = false;
+                var currentlyPopping = false;
+                var popToRootPending = false;
+                var userInstigated = false;
 
                 this.WhenAnyObservable(x => x.Router.NavigationChanged)
                     .Where(_ => Router.NavigationStack.Count == 0)
@@ -116,7 +116,7 @@ public RoutedViewHost()
                     .SelectMany(_ => PageForViewModel(Router.GetCurrentViewModel()))
                     .SelectMany(async page =>
                     {
-                        bool animated = true;
+                        var animated = true;
                         var attribute = page.GetType().GetCustomAttribute<DisableAnimationAttribute>();
                         if (attribute is not null)
                         {
@@ -184,9 +184,7 @@ public RoutedViewHost()
             Router = screen.Router;
 
             this.WhenAnyValue(x => x.Router)
-                .SelectMany(router =>
-                {
-                    return router.NavigationStack
+                .SelectMany(router => router!.NavigationStack
                         .ToObservable()
                         .Select(x => (Page)ViewLocator.Current.ResolveView(x)!)
                         .SelectMany(x => PushAsync(x).ToObservable())
@@ -200,8 +198,7 @@ public RoutedViewHost()
 
                             ((IViewFor)CurrentPage).ViewModel = vm;
                             CurrentPage.Title = vm.UrlPathSegment;
-                        });
-                })
+                        }))
                 .Subscribe();
         }
 
diff --git a/src/ReactiveUI/Activation/ViewForMixins.cs b/src/ReactiveUI/Activation/ViewForMixins.cs
index 7d16e05b27..5fc10de5e1 100644
--- a/src/ReactiveUI/Activation/ViewForMixins.cs
+++ b/src/ReactiveUI/Activation/ViewForMixins.cs
@@ -25,7 +25,7 @@ public static class ViewForMixins
                           .GetServices<IActivationForViewFetcher?>()
                           .Aggregate((count: 0, viewFetcher: default(IActivationForViewFetcher?)), (acc, x) =>
                           {
-                              int score = x?.GetAffinityForView(t) ?? 0;
+                              var score = x?.GetAffinityForView(t) ?? 0;
                               return score > acc.count ? (score, x) : acc;
                           }).viewFetcher, RxApp.SmallCacheLimit);
 
diff --git a/src/ReactiveUI/Bindings/Command/CommandBinderImplementation.cs b/src/ReactiveUI/Bindings/Command/CommandBinderImplementation.cs
index 29535c2430..f4a8c21250 100644
--- a/src/ReactiveUI/Bindings/Command/CommandBinderImplementation.cs
+++ b/src/ReactiveUI/Bindings/Command/CommandBinderImplementation.cs
@@ -62,7 +62,7 @@ public IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TCon
             var controlExpression = Reflection.Rewrite(controlProperty.Body);
             var source = Reflection.ViewModelWhenAnyValue(viewModel, view, vmExpression).Cast<TProp>();
 
-            IDisposable bindingDisposable = BindCommandInternal(source, view, controlExpression, Observable.Defer(() => Observable.Return(withParameter())), toEvent ?? string.Empty, cmd =>
+            var bindingDisposable = BindCommandInternal(source, view, controlExpression, Observable.Defer(() => Observable.Return(withParameter())), toEvent ?? string.Empty, cmd =>
             {
                 if (!(cmd is IReactiveCommand rc))
                 {
@@ -127,7 +127,7 @@ public IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TCon
             var controlExpression = Reflection.Rewrite(controlProperty.Body);
             var source = Reflection.ViewModelWhenAnyValue(viewModel, view, vmExpression).Cast<TProp>();
 
-            IDisposable bindingDisposable = BindCommandInternal(source, view, controlExpression, withParameter, toEvent);
+            var bindingDisposable = BindCommandInternal(source, view, controlExpression, withParameter, toEvent);
 
             return new ReactiveBinding<TView, TProp>(
                  view,
@@ -148,7 +148,7 @@ private static IDisposable BindCommandInternal<TView, TProp, TParam>(
             where TView : class, IViewFor
             where TProp : ICommand
         {
-            IDisposable disposable = Disposable.Empty;
+            var disposable = Disposable.Empty;
 
             var bindInfo = source.CombineLatest(
                 view.SubscribeToExpressionChain<TView, object?>(controlExpression, false, false, RxApp.SuppressViewCommandBindingMessage).Select(x => x.Value),
diff --git a/src/ReactiveUI/Bindings/Command/CreatesCommandBinding.cs b/src/ReactiveUI/Bindings/Command/CreatesCommandBinding.cs
index 1ca7325fc8..725010b51e 100644
--- a/src/ReactiveUI/Bindings/Command/CreatesCommandBinding.cs
+++ b/src/ReactiveUI/Bindings/Command/CreatesCommandBinding.cs
@@ -22,7 +22,7 @@ internal class CreatesCommandBinding
                 return Locator.Current.GetServices<ICreatesCommandBinding>()
                     .Aggregate((score: 0, binding: (ICreatesCommandBinding?)null), (acc, x) =>
                     {
-                        int score = x.GetAffinityForObject(t, false);
+                        var score = x.GetAffinityForObject(t, false);
                         return (score > acc.score) ? (score, x) : acc;
                     }).binding;
             }, RxApp.SmallCacheLimit);
@@ -34,7 +34,7 @@ internal class CreatesCommandBinding
                 return Locator.Current.GetServices<ICreatesCommandBinding>()
                     .Aggregate((score: 0, binding: (ICreatesCommandBinding?)null), (acc, x) =>
                     {
-                        int score = x.GetAffinityForObject(t, true);
+                        var score = x.GetAffinityForObject(t, true);
                         return (score > acc.score) ? (score, x) : acc;
                     }).binding;
             }, RxApp.SmallCacheLimit);
diff --git a/src/ReactiveUI/Bindings/ISetMethodBindingConverter.cs b/src/ReactiveUI/Bindings/ISetMethodBindingConverter.cs
index c7f69709b7..0b7c9ebdde 100644
--- a/src/ReactiveUI/Bindings/ISetMethodBindingConverter.cs
+++ b/src/ReactiveUI/Bindings/ISetMethodBindingConverter.cs
@@ -24,7 +24,7 @@ public interface ISetMethodBindingConverter : IEnableLogger
         /// <param name="toType">The target type to convert to.</param>
         /// <returns>A positive integer if PerformSet is supported,
         /// zero or a negative value otherwise.</returns>
-        int GetAffinityForObjects(Type fromType, Type toType);
+        int GetAffinityForObjects(Type? fromType, Type? toType);
 
         /// <summary>
         /// Convert a given object to the specified type.
diff --git a/src/ReactiveUI/Bindings/Property/IPropertyBinderImplementation.cs b/src/ReactiveUI/Bindings/Property/IPropertyBinderImplementation.cs
index d130b27c7b..346d054ea4 100644
--- a/src/ReactiveUI/Bindings/Property/IPropertyBinderImplementation.cs
+++ b/src/ReactiveUI/Bindings/Property/IPropertyBinderImplementation.cs
@@ -224,8 +224,8 @@ IReactiveBinding<TView, TOut> OneWayBind<TViewModel, TView, TProp, TOut>(
 
         /// <summary>
         /// BindTo takes an Observable stream and applies it to a target
-        /// property. Conceptually it is similar to <c>Subscribe(x =&gt;
-        /// target.property = x)</c>, but allows you to use child properties
+        /// property. Conceptually it is similar to. <code>Subscribe(x =&gt;
+        /// target.property = x)</code>, but allows you to use child properties
         /// without the null checks.
         /// </summary>
         /// <typeparam name="TValue">The value type.</typeparam>
diff --git a/src/ReactiveUI/Bindings/Property/PropertyBinderImplementation.cs b/src/ReactiveUI/Bindings/Property/PropertyBinderImplementation.cs
index eda407f2cf..162d265cfc 100644
--- a/src/ReactiveUI/Bindings/Property/PropertyBinderImplementation.cs
+++ b/src/ReactiveUI/Bindings/Property/PropertyBinderImplementation.cs
@@ -20,37 +20,27 @@ namespace ReactiveUI
     /// <summary>
     /// Provides methods to bind properties to observables.
     /// </summary>
-    [SuppressMessage("StyleCop.CSharp.SpacingRules", "SA1011:Closing square brackets should be spaced correctly", Justification = "nullable object array.")]
     public class PropertyBinderImplementation : IPropertyBinderImplementation
     {
         private static readonly MemoizingMRUCache<(Type fromType, Type toType), IBindingTypeConverter?> _typeConverterCache = new(
-            (types, _) =>
-            {
-                return Locator.Current.GetServices<IBindingTypeConverter?>()
+            (types, _) => Locator.Current.GetServices<IBindingTypeConverter?>()
                     .Aggregate((currentAffinity: -1, currentBinding: default(IBindingTypeConverter)), (acc, x) =>
                     {
                         var score = x?.GetAffinityForObjects(types.fromType, types.toType) ?? -1;
                         return score > acc.currentAffinity && score > 0 ? (score, x) : acc;
-                    }).currentBinding;
-            },
+                    }).currentBinding,
             RxApp.SmallCacheLimit);
 
-        private static readonly MemoizingMRUCache<(Type fromType, Type toType), ISetMethodBindingConverter?> _setMethodCache = new(
-            (type, _) =>
-            {
-                return Locator.Current.GetServices<ISetMethodBindingConverter>()
+        private static readonly MemoizingMRUCache<(Type? fromType, Type? toType), ISetMethodBindingConverter?> _setMethodCache = new(
+            (type, _) => Locator.Current.GetServices<ISetMethodBindingConverter>()
                     .Aggregate((currentAffinity: -1, currentBinding: default(ISetMethodBindingConverter)), (acc, x) =>
                     {
                         var score = x.GetAffinityForObjects(type.fromType, type.toType);
                         return score > acc.currentAffinity && score > 0 ? (score, x) : acc;
-                    }).currentBinding;
-            },
+                    }).currentBinding,
             RxApp.SmallCacheLimit);
 
-        static PropertyBinderImplementation()
-        {
-            RxApp.EnsureInitialized();
-        }
+        static PropertyBinderImplementation() => RxApp.EnsureInitialized();
 
         private delegate bool OutFunc<in T1, T2>(T1 t1, out T2 t2);
 
@@ -78,7 +68,7 @@ static PropertyBinderImplementation()
 
             bool VmToViewFunc(TVMProp? vmValue, out TVProp vValue)
             {
-                var result = vmToViewConverter.TryConvert(vmValue, typeof(TVProp), conversionHint, out object? tmp);
+                var result = vmToViewConverter.TryConvert(vmValue, typeof(TVProp), conversionHint, out var tmp);
 
                 vValue = result && tmp != null ? (TVProp)tmp : default!;
                 return result;
@@ -86,7 +76,7 @@ bool VmToViewFunc(TVMProp? vmValue, out TVProp vValue)
 
             bool ViewToVmFunc(TVProp vValue, out TVMProp? vmValue)
             {
-                var result = viewToVMConverter.TryConvert(vValue, typeof(TVMProp?), conversionHint, out object? tmp);
+                var result = viewToVMConverter.TryConvert(vValue, typeof(TVMProp?), conversionHint, out var tmp);
 
                 vmValue = result && tmp != null ? (TVMProp?)tmp : default;
                 return result;
@@ -180,15 +170,7 @@ public IReactiveBinding<TView, TVProp> OneWayBind<TViewModel, TView, TVMProp, TV
             }
 
             var source = Reflection.ViewModelWhenAnyValue(viewModel, view, vmExpression)
-                    .SelectMany(x =>
-                    {
-                        if (!converter.TryConvert(x, viewType, conversionHint, out object? tmp))
-                        {
-                            return Observable<object>.Empty;
-                        }
-
-                        return Observable.Return(tmp);
-                    });
+                    .SelectMany(x => !converter.TryConvert(x, viewType, conversionHint, out var tmp) ? Observable<object>.Empty : Observable.Return(tmp));
 
             var (disposable, obs) = BindToDirect<TView, TVProp, object?>(source, view, viewExpression);
 
@@ -264,27 +246,17 @@ public IDisposable BindTo<TValue, TTarget, TTValue>(
                 throw new ArgumentException($"Can't convert {typeof(TValue)} to {typeof(TTValue)}. To fix this, register a IBindingTypeConverter");
             }
 
-            var source = observedChange.SelectMany(x =>
-            {
-                if (!converter.TryConvert(x, typeof(TTValue?), conversionHint, out var tmp))
-                {
-                    return Observable<object>.Empty;
-                }
-
-                return Observable.Return(tmp);
-            });
+            var source = observedChange.SelectMany(x => !converter.TryConvert(x, typeof(TTValue?), conversionHint, out var tmp) ? Observable<object>.Empty : Observable.Return(tmp));
 
             var (disposable, _) = BindToDirect<TTarget, TTValue?, object?>(source, target, viewExpression);
 
             return disposable;
         }
 
-        internal static IBindingTypeConverter? GetConverterForTypes(Type lhs, Type rhs)
-        {
-            return _typeConverterCache.Get((lhs, rhs));
-        }
+        internal static IBindingTypeConverter? GetConverterForTypes(Type lhs, Type rhs) =>
+            _typeConverterCache.Get((lhs, rhs));
 
-        private static Func<object?, object?, object?[]?, object?>? GetSetConverter(Type? fromType, Type targetType)
+        private static Func<object?, object?, object?[]?, object?>? GetSetConverter(Type? fromType, Type? targetType)
         {
             if (fromType == null)
             {
@@ -293,12 +265,7 @@ public IDisposable BindTo<TValue, TTarget, TTValue>(
 
             var setter = _setMethodCache.Get((fromType, targetType));
 
-            if (setter == null)
-            {
-                return null;
-            }
-
-            return setter.PerformSet;
+            return setter == null ? null : setter.PerformSet;
         }
 
         private (IDisposable disposable, IObservable<TValue> value) BindToDirect<TTarget, TValue, TObs>(
@@ -310,7 +277,7 @@ public IDisposable BindTo<TValue, TTarget, TTValue>(
             var defaultSetter = Reflection.GetValueSetterOrThrow(viewExpression.GetMemberInfo());
             var defaultGetter = Reflection.GetValueFetcherOrThrow(viewExpression.GetMemberInfo());
 
-            object? SetThenGet(object paramTarget, object? paramValue, object?[]? paramParams)
+            object? SetThenGet(object? paramTarget, object? paramValue, object?[]? paramParams)
             {
                 var converter = GetSetConverter(paramValue?.GetType(), viewExpression.Type);
 
@@ -345,14 +312,7 @@ public IDisposable BindTo<TValue, TTarget, TTValue>(
                     {
                         var value = SetThenGet(x.host, x.val, viewExpression.GetArgumentsArray());
 
-                        if (value == null)
-                        {
-#pragma warning disable CS8603 // Possible null reference return.
-                            return default;
-#pragma warning restore CS8603 // Possible null reference return.
-                        }
-
-                        return (TValue)value;
+                        return value == null ? default : (TValue)value;
                     })!;
             }
 
@@ -369,22 +329,16 @@ private bool EvalBindingHooks<TViewModel, TView>(TViewModel? viewModel, TView vi
                 throw new ArgumentNullException(nameof(view));
             }
 
-            Func<IObservedChange<object, object?>[]> vmFetcher;
-            if (vmExpression != null)
-            {
-                vmFetcher = () =>
+            Func<IObservedChange<object, object?>[]> vmFetcher = vmExpression != null
+                ? (() =>
                 {
                     Reflection.TryGetAllValuesForPropertyChain(out var fetchedValues, viewModel, vmExpression.GetExpressionChain());
                     return fetchedValues;
-                };
-            }
-            else
-            {
-                vmFetcher = () => new IObservedChange<object, object?>[]
+                })
+                : (() => new IObservedChange<object, object?>[]
                 {
                     new ObservedChange<object, object?>(null!, null!, viewModel)
-                };
-            }
+                });
 
             var vFetcher = new Func<IObservedChange<object, object?>[]>(() =>
             {
@@ -413,8 +367,8 @@ private bool EvalBindingHooks<TViewModel, TView>(TViewModel? viewModel, TView vi
             IObservable<TDontCare>? signalViewUpdate,
             OutFunc<TVMProp?, TVProp> vmToViewConverter,
             OutFunc<TVProp, TVMProp?> viewToVmConverter)
-            where TView : class, IViewFor
             where TViewModel : class
+            where TView : class, IViewFor
         {
             if (vmProperty == null)
             {
@@ -432,7 +386,7 @@ private bool EvalBindingHooks<TViewModel, TView>(TViewModel? viewModel, TView vi
 
             var signalObservable = signalViewUpdate != null
                                        ? signalViewUpdate.Select(_ => false)
-                                       : view.WhenAnyDynamic(viewExpression, x => (TVProp)x.Value).Select(_ => false);
+                                       : view.WhenAnyDynamic(viewExpression, x => (TVProp?)x.Value).Select(_ => false);
 
             var somethingChanged = Observable.Merge(
                                                     Reflection.ViewModelWhenAnyValue(viewModel, view, vmExpression).Select(_ => true),
@@ -440,30 +394,16 @@ private bool EvalBindingHooks<TViewModel, TView>(TViewModel? viewModel, TView vi
                                                     signalObservable);
 
             var changeWithValues = somethingChanged.Select<bool, (bool isValid, object? view, bool isViewModel)>(isVm =>
-            {
-                if (!Reflection.TryGetValueForPropertyChain(out TVMProp vmValue, view.ViewModel, vmExpression.GetExpressionChain()) ||
-                    !Reflection.TryGetValueForPropertyChain(out TVProp vValue, view, viewExpression.GetExpressionChain()))
-                {
-                    return (false, null, false);
-                }
-
-                if (isVm)
-                {
-                    if (!vmToViewConverter(vmValue, out TVProp vmAsView) || EqualityComparer<TVProp>.Default.Equals(vValue, vmAsView))
-                    {
-                        return (false, null, false);
-                    }
-
-                    return (true, vmAsView, isVm);
-                }
-
-                if (!viewToVmConverter(vValue, out TVMProp? vAsViewModel) || EqualityComparer<TVMProp?>.Default.Equals(vmValue, vAsViewModel))
-                {
-                    return (false, null, false);
-                }
-
-                return (true, vAsViewModel, isVm);
-            });
+            !Reflection.TryGetValueForPropertyChain(out TVMProp vmValue, view.ViewModel, vmExpression.GetExpressionChain()) ||
+                    !Reflection.TryGetValueForPropertyChain(out TVProp vValue, view, viewExpression.GetExpressionChain())
+                    ? (false, null, false)
+                    : isVm
+                    ? !vmToViewConverter(vmValue, out var vmAsView) || EqualityComparer<TVProp>.Default.Equals(vValue, vmAsView)
+                        ? (false, null, false)
+                        : (true, vmAsView, isVm)
+                    : !viewToVmConverter(vValue, out var vAsViewModel) || EqualityComparer<TVMProp?>.Default.Equals(vmValue, vAsViewModel)
+                    ? (false, null, false)
+                    : (true, vAsViewModel, isVm));
 
             var ret = EvalBindingHooks(viewModel, view, vmExpression, viewExpression, BindingDirection.TwoWay);
             if (!ret)
@@ -471,13 +411,13 @@ private bool EvalBindingHooks<TViewModel, TView>(TViewModel? viewModel, TView vi
                 return null!;
             }
 
-            IObservable<(object? view, bool isViewModel)> changes = changeWithValues
+            var changes = changeWithValues
                 .Where(value => value.isValid)
                 .Select(value => (value.view, value.isViewModel))
                 .Publish()
                 .RefCount();
 
-            IDisposable disposable = changes.Subscribe(isVmWithLatestValue =>
+            var disposable = changes.Subscribe(isVmWithLatestValue =>
             {
                 if (isVmWithLatestValue.isViewModel)
                 {
diff --git a/src/ReactiveUI/Bindings/Property/PropertyBindingMixins.cs b/src/ReactiveUI/Bindings/Property/PropertyBindingMixins.cs
index 86a58059e0..ac5ec1a067 100644
--- a/src/ReactiveUI/Bindings/Property/PropertyBindingMixins.cs
+++ b/src/ReactiveUI/Bindings/Property/PropertyBindingMixins.cs
@@ -33,12 +33,12 @@ static PropertyBindingMixins()
         /// <param name="viewModel">The instance of the view model to bind.</param>
         /// <param name="vmProperty">
         /// An expression indicating the property that is bound on the view model.
-        /// This can be a chain of properties of the form. <code>vm =&gt; vm.Foo.Bar.Baz</code>
+        /// This can be a chain of properties of the form. <c>vm =&gt; vm.Foo.Bar.Baz</c>
         /// and the binder will attempt to subscribe to changes on each recursively.
         /// </param>
         /// <param name="viewProperty">
         /// The property on the view that is to be bound.
-        /// This can be a chain of properties of the form. <code>view => view.Foo.Bar.Baz</code>
+        /// This can be a chain of properties of the form. <c>view => view.Foo.Bar.Baz</c>
         /// and the binder will attempt to set the last one each time the view model property is updated.
         /// </param>
         /// <param name="conversionHint">
@@ -93,12 +93,12 @@ static PropertyBindingMixins()
         /// <param name="viewModel">The instance of the view model to bind.</param>
         /// <param name="vmProperty">
         /// An expression indicating the property that is bound on the view model.
-        /// This can be a chain of properties of the form. <code>vm =&gt; vm.Foo.Bar.Baz</code>
+        /// This can be a chain of properties of the form. <c>vm =&gt; vm.Foo.Bar.Baz</c>
         /// and the binder will attempt to subscribe to changes on each recursively.
         /// </param>
         /// <param name="viewProperty">
         /// The property on the view that is to be bound.
-        /// This can be a chain of properties of the form. <code>view => view.Foo.Bar.Baz</code>
+        /// This can be a chain of properties of the form. <c>view => view.Foo.Bar.Baz</c>
         /// and the binder will attempt to set the last one each time the view model property is updated.
         /// </param>
         /// <param name="signalViewUpdate">
@@ -146,12 +146,12 @@ static PropertyBindingMixins()
         /// <param name="viewModel">The instance of the view model to bind.</param>
         /// <param name="vmProperty">
         /// An expression indicating the property that is bound on the view model.
-        /// This can be a chain of properties of the form. <code>vm =&gt; vm.Foo.Bar.Baz</code>
+        /// This can be a chain of properties of the form. <c>vm =&gt; vm.Foo.Bar.Baz</c>
         /// and the binder will attempt to subscribe to changes on each recursively.
         /// </param>
         /// <param name="viewProperty">
         /// The property on the view that is to be bound.
-        /// This can be a chain of properties of the form. <code>view => view.Foo.Bar.Baz</code>
+        /// This can be a chain of properties of the form. <c>view => view.Foo.Bar.Baz</c>
         /// and the binder will attempt to set the last one each time the view model property is updated.
         /// </param>
         /// <param name="vmToViewConverter">
@@ -191,12 +191,12 @@ static PropertyBindingMixins()
         /// <param name="viewModel">The instance of the view model to bind.</param>
         /// <param name="vmProperty">
         /// An expression indicating the property that is bound on the view model.
-        /// This can be a chain of properties of the form. <code>vm =&gt; vm.Foo.Bar.Baz</code>
+        /// This can be a chain of properties of the form. <c>vm =&gt; vm.Foo.Bar.Baz</c>
         /// and the binder will attempt to subscribe to changes on each recursively.
         /// </param>
         /// <param name="viewProperty">
         /// The property on the view that is to be bound.
-        /// This can be a chain of properties of the form. <code>view => view.Foo.Bar.Baz</code>
+        /// This can be a chain of properties of the form. <c>view => view.Foo.Bar.Baz</c>
         /// and the binder will attempt to set the last one each time the view model property is updated.
         /// </param>
         /// <param name="signalViewUpdate">
@@ -236,7 +236,7 @@ static PropertyBindingMixins()
         /// <typeparam name="TVMProp">The type of view model property.</typeparam>
         /// <typeparam name="TVProp">The type of the property bound on the view.</typeparam>
         /// <param name="view">
-        /// The instance of the view object which is bound. Usually, it is the. <code>this</code>
+        /// The instance of the view object which is bound. Usually, it is the. <c>this</c>
         /// instance.
         /// </param>
         /// <param name="viewModel">
@@ -244,12 +244,12 @@ static PropertyBindingMixins()
         /// It is usually set to the <see cref="IViewFor.ViewModel"/> property of the <paramref name="view"/>.</param>
         /// <param name="vmProperty">
         /// An expression indicating the property that is bound on the view model.
-        /// This can be a chain of properties of the form. <code>vm => vm.Foo.Bar.Baz</code>
+        /// This can be a chain of properties of the form. <c>vm => vm.Foo.Bar.Baz</c>
         /// and the binder will attempt to subscribe to changes on each recursively.
         /// </param>
         /// <param name="viewProperty">
         /// The property on the view that is to be bound.
-        /// This can be a chain of properties of the form. <code>view => view.Foo.Bar.Baz</code>
+        /// This can be a chain of properties of the form. <c>view => view.Foo.Bar.Baz</c>
         /// and the binder will attempt to set the last one each time the view model property is updated.
         /// </param>
         /// <param name="conversionHint">
@@ -323,8 +323,8 @@ public static IReactiveBinding<TView, TOut> OneWayBind<TViewModel, TView, TProp,
 
         /// <summary>
         /// BindTo takes an Observable stream and applies it to a target
-        /// property. Conceptually it is similar to <c>Subscribe(x =&gt;
-        /// target.property = x)</c>, but allows you to use child properties
+        /// property. Conceptually it is similar to. <code>Subscribe(x =&gt;
+        /// target.property = x)</code>, but allows you to use child properties
         /// without the null checks.
         /// </summary>
         /// <typeparam name="TValue">The source type.</typeparam>
diff --git a/src/ReactiveUI/Comparers/ChainedComparer.cs b/src/ReactiveUI/Comparers/ChainedComparer.cs
index c295bc0394..42e6788f27 100644
--- a/src/ReactiveUI/Comparers/ChainedComparer.cs
+++ b/src/ReactiveUI/Comparers/ChainedComparer.cs
@@ -24,7 +24,7 @@ public ChainedComparer(IComparer<T>? parent, Comparison<T> comparison)
         public int Compare(T x, T y)
 #pragma warning restore CS8767 // Nullability of reference types in type of parameter doesn't match implicitly implemented member (possibly because of nullability attributes).
         {
-            int parentResult = _parent?.Compare(x, y) ?? 0;
+            var parentResult = _parent?.Compare(x, y) ?? 0;
 
             if (x is null && y is null)
             {
diff --git a/src/ReactiveUI/Expression/ExpressionRewriter.cs b/src/ReactiveUI/Expression/ExpressionRewriter.cs
index 37e9c2d4e9..2eceda0c7a 100644
--- a/src/ReactiveUI/Expression/ExpressionRewriter.cs
+++ b/src/ReactiveUI/Expression/ExpressionRewriter.cs
@@ -66,8 +66,8 @@ protected override Expression VisitBinary(BinaryExpression node)
                 throw new NotSupportedException("Array index expressions are only supported with constants.");
             }
 
-            Expression left = Visit(node.Left);
-            Expression right = Visit(node.Right);
+            var left = Visit(node.Left);
+            var right = Visit(node.Right);
 
             // Translate arrayindex into normal index expression
             return Expression.MakeIndex(left, left.Type.GetRuntimeProperty("Item"), new[] { right });
@@ -77,7 +77,7 @@ protected override Expression VisitUnary(UnaryExpression node)
         {
             if (node.NodeType == ExpressionType.ArrayLength && node.Operand is not null)
             {
-                Expression expression = Visit(node.Operand);
+                var expression = Visit(node.Operand);
 
                 var memberInfo = expression.Type.GetRuntimeProperty("Length");
 
@@ -116,7 +116,7 @@ protected override Expression VisitMethodCall(MethodCallExpression node)
                 throw new ArgumentException("The Method call does not point towards an object.", nameof(node));
             }
 
-            Expression instance = Visit(node.Object);
+            var instance = Visit(node.Object);
             IEnumerable<Expression> arguments = Visit(node.Arguments);
 
             // Translate call to get_Item into normal index expression
diff --git a/src/ReactiveUI/Expression/Reflection.cs b/src/ReactiveUI/Expression/Reflection.cs
index a81ce8c6d6..f4d2b893bd 100644
--- a/src/ReactiveUI/Expression/Reflection.cs
+++ b/src/ReactiveUI/Expression/Reflection.cs
@@ -20,19 +20,16 @@ namespace ReactiveUI
     /// <summary>
     /// Helper class for handling Reflection amd Expression tree related items.
     /// </summary>
-    [SuppressMessage("StyleCop.CSharp.SpacingRules", "SA1011:Closing square brackets should be spaced correctly", Justification = "nullable object array.")]
     public static class Reflection
     {
-        private static readonly ExpressionRewriter expressionRewriter = new ExpressionRewriter();
+        private static readonly ExpressionRewriter _expressionRewriter = new();
 
-        private static readonly MemoizingMRUCache<string, Type?> _typeCache = new MemoizingMRUCache<string, Type?>(
-            (type, _) =>
-            {
-                return Type.GetType(
+        private static readonly MemoizingMRUCache<string, Type?> _typeCache = new(
+            (type, _) => Type.GetType(
                                     type,
                                     assemblyName =>
                                     {
-                                        var assembly = AppDomain.CurrentDomain.GetAssemblies().FirstOrDefault(z => z.FullName == assemblyName.FullName);
+                                        var assembly = Array.Find(AppDomain.CurrentDomain.GetAssemblies(), z => z.FullName == assemblyName.FullName);
                                         if (assembly != null)
                                         {
                                             return assembly;
@@ -48,8 +45,7 @@ public static class Reflection
                                         }
                                     },
                                     null,
-                                    false);
-            },
+                                    false),
             20);
 
         /// <summary>
@@ -57,10 +53,7 @@ public static class Reflection
         /// </summary>
         /// <param name="expression">The expression to rewrite.</param>
         /// <returns>The rewritten expression.</returns>
-        public static Expression Rewrite(Expression expression)
-        {
-            return expressionRewriter.Visit(expression);
-        }
+        public static Expression Rewrite(Expression? expression) => _expressionRewriter.Visit(expression);
 
         /// <summary>
         /// Will convert a Expression which points towards a property
@@ -70,7 +63,7 @@ public static Expression Rewrite(Expression expression)
         /// </summary>
         /// <param name="expression">The expression to generate the property names from.</param>
         /// <returns>A string form for the property the expression is pointing to.</returns>
-        public static string ExpressionToPropertyNames(Expression expression)
+        public static string ExpressionToPropertyNames(Expression? expression)
         {
             if (expression == null)
             {
@@ -79,7 +72,7 @@ public static string ExpressionToPropertyNames(Expression expression)
 
             StringBuilder sb = new StringBuilder();
 
-            foreach (Expression exp in expression.GetExpressionChain())
+            foreach (var exp in expression.GetExpressionChain())
             {
                 if (exp.NodeType != ExpressionType.Parameter)
                 {
@@ -118,26 +111,21 @@ public static string ExpressionToPropertyNames(Expression expression)
         /// </summary>
         /// <param name="member">The member info to convert.</param>
         /// <returns>A Func that takes in the object/indexes and returns the value.</returns>
-        public static Func<object, object?[]?, object?>? GetValueFetcherForProperty(MemberInfo? member)
+        public static Func<object?, object?[]?, object?>? GetValueFetcherForProperty(MemberInfo? member)
         {
             if (member is null)
             {
                 throw new ArgumentNullException(nameof(member));
             }
 
-            FieldInfo? field = member as FieldInfo;
+            var field = member as FieldInfo;
             if (field != null)
             {
                 return (obj, _) => field.GetValue(obj) ?? throw new InvalidOperationException();
             }
 
-            PropertyInfo? property = member as PropertyInfo;
-            if (property != null)
-            {
-                return property.GetValue;
-            }
-
-            return null;
+            var property = member as PropertyInfo;
+            return property!.GetValue;
         }
 
         /// <summary>
@@ -148,7 +136,7 @@ public static string ExpressionToPropertyNames(Expression expression)
         /// </summary>
         /// <param name="member">The member info to convert.</param>
         /// <returns>A Func that takes in the object/indexes and returns the value.</returns>
-        public static Func<object, object?[]?, object?> GetValueFetcherOrThrow(MemberInfo? member)
+        public static Func<object?, object?[]?, object?> GetValueFetcherOrThrow(MemberInfo? member)
         {
             if (member is null)
             {
@@ -157,12 +145,7 @@ public static string ExpressionToPropertyNames(Expression expression)
 
             var ret = GetValueFetcherForProperty(member);
 
-            if (ret == null)
-            {
-                throw new ArgumentException($"Type '{member.DeclaringType}' must have a property '{member.Name}'");
-            }
-
-            return ret;
+            return ret ?? throw new ArgumentException($"Type '{member.DeclaringType}' must have a property '{member.Name}'");
         }
 
         /// <summary>
@@ -173,7 +156,7 @@ public static string ExpressionToPropertyNames(Expression expression)
         /// </summary>
         /// <param name="member">The member info to convert.</param>
         /// <returns>A Func that takes in the object/indexes and sets the value.</returns>
-        public static Action<object, object?, object?[]?> GetValueSetterForProperty(MemberInfo? member)
+        public static Action<object?, object?, object?[]?> GetValueSetterForProperty(MemberInfo? member)
         {
             if (member is null)
             {
@@ -187,12 +170,7 @@ public static string ExpressionToPropertyNames(Expression expression)
             }
 
             PropertyInfo? property = member as PropertyInfo;
-            if (property != null)
-            {
-                return property.SetValue;
-            }
-
-            return null!;
+            return property!.SetValue;
         }
 
         /// <summary>
@@ -203,7 +181,7 @@ public static string ExpressionToPropertyNames(Expression expression)
         /// </summary>
         /// <param name="member">The member info to convert.</param>
         /// <returns>A Func that takes in the object/indexes and sets the value.</returns>
-        public static Action<object, object?, object?[]?>? GetValueSetterOrThrow(MemberInfo? member)
+        public static Action<object?, object?, object?[]?>? GetValueSetterOrThrow(MemberInfo? member)
         {
             if (member is null)
             {
@@ -212,12 +190,7 @@ public static string ExpressionToPropertyNames(Expression expression)
 
             var ret = GetValueSetterForProperty(member);
 
-            if (ret == null)
-            {
-                throw new ArgumentException($"Type '{member.DeclaringType}' must have a property '{member.Name}'");
-            }
-
-            return ret;
+            return ret ?? throw new ArgumentException($"Type '{member.DeclaringType}' must have a property '{member.Name}'");
         }
 
         /// <summary>
@@ -234,7 +207,7 @@ public static string ExpressionToPropertyNames(Expression expression)
         public static bool TryGetValueForPropertyChain<TValue>(out TValue changeValue, object? current, IEnumerable<Expression> expressionChain)
         {
             var expressions = expressionChain.ToList();
-            foreach (Expression expression in expressions.SkipLast(1))
+            foreach (var expression in expressions.SkipLast(1))
             {
                 if (current == null)
                 {
@@ -251,12 +224,8 @@ public static bool TryGetValueForPropertyChain<TValue>(out TValue changeValue, o
                 return false;
             }
 
-            Expression lastExpression = expressions.Last();
-#pragma warning disable CS8601 // Possible null reference assignment.
-#pragma warning disable CS8605 // Unboxing a possibly null value.
+            var lastExpression = expressions.Last();
             changeValue = (TValue)GetValueFetcherOrThrow(lastExpression.GetMemberInfo())(current, lastExpression.GetArgumentsArray())!;
-#pragma warning restore CS8605 // Unboxing a possibly null value.
-#pragma warning restore CS8601 // Possible null reference assignment.
             return true;
         }
 
@@ -273,11 +242,11 @@ public static bool TryGetValueForPropertyChain<TValue>(out TValue changeValue, o
         /// <returns>If the value was successfully retrieved or not.</returns>
         public static bool TryGetAllValuesForPropertyChain(out IObservedChange<object, object?>[] changeValues, object? current, IEnumerable<Expression> expressionChain)
         {
-            int currentIndex = 0;
+            var currentIndex = 0;
             var expressions = expressionChain.ToList();
             changeValues = new IObservedChange<object, object>[expressions.Count];
 
-            foreach (Expression expression in expressions.SkipLast(1))
+            foreach (var expression in expressions.SkipLast(1))
             {
                 if (current == null)
                 {
@@ -287,9 +256,7 @@ public static bool TryGetAllValuesForPropertyChain(out IObservedChange<object, o
 
                 var sender = current;
                 current = GetValueFetcherOrThrow(expression.GetMemberInfo())(current, expression.GetArgumentsArray());
-#pragma warning disable CS8604 // Possible null reference argument.
                 changeValues[currentIndex] = new ObservedChange<object, object?>(sender, expression, current);
-#pragma warning restore CS8604 // Possible null reference argument.
                 currentIndex++;
             }
 
@@ -299,11 +266,8 @@ public static bool TryGetAllValuesForPropertyChain(out IObservedChange<object, o
                 return false;
             }
 
-            Expression lastExpression = expressions.Last();
-#pragma warning disable CS8604 // Possible null reference argument.
+            var lastExpression = expressions.Last();
             changeValues[currentIndex] = new ObservedChange<object, object?>(current, lastExpression, GetValueFetcherOrThrow(lastExpression.GetMemberInfo())(current, lastExpression.GetArgumentsArray()));
-#pragma warning restore CS8604 // Possible null reference argument.
-
             return true;
         }
 
@@ -323,7 +287,7 @@ public static bool TryGetAllValuesForPropertyChain(out IObservedChange<object, o
         public static bool TrySetValueToPropertyChain<TValue>(object? target, IEnumerable<Expression> expressionChain, TValue value, bool shouldThrow = true)
         {
             var expressions = expressionChain.ToList();
-            foreach (Expression expression in expressions.SkipLast(1))
+            foreach (var expression in expressions.SkipLast(1))
             {
                 var getter = shouldThrow ?
                     GetValueFetcherOrThrow(expression.GetMemberInfo()) :
@@ -340,8 +304,8 @@ public static bool TrySetValueToPropertyChain<TValue>(object? target, IEnumerabl
                 return false;
             }
 
-            Expression lastExpression = expressions.Last();
-            Action<object, object?, object?[]?>? setter = shouldThrow ?
+            var lastExpression = expressions.Last();
+            var setter = shouldThrow ?
                 GetValueSetterOrThrow(lastExpression.GetMemberInfo()) :
                 GetValueSetterForProperty(lastExpression.GetMemberInfo());
 
@@ -364,13 +328,8 @@ public static bool TrySetValueToPropertyChain<TValue>(object? target, IEnumerabl
         /// <exception cref="TypeLoadException">If we were unable to find the type.</exception>
         public static Type? ReallyFindType(string? type, bool throwOnFailure)
         {
-            Type? ret = _typeCache.Get(type ?? string.Empty);
-            if (ret != null || !throwOnFailure)
-            {
-                return ret;
-            }
-
-            throw new TypeLoadException();
+            var ret = _typeCache.Get(type ?? string.Empty);
+            return ret != null || !throwOnFailure ? ret : throw new TypeLoadException();
         }
 
         /// <summary>
@@ -387,8 +346,8 @@ public static Type GetEventArgsTypeForEvent(Type type, string eventName)
                 throw new ArgumentNullException(nameof(type));
             }
 
-            Type ti = type;
-            EventInfo? ei = ti.GetRuntimeEvent(eventName);
+            var ti = type;
+            var ei = ti.GetRuntimeEvent(eventName);
             if (ei == null || ei.EventHandlerType == null)
             {
                 throw new Exception($"Couldn't find {type.FullName}.{eventName}");
@@ -408,17 +367,17 @@ public static Type GetEventArgsTypeForEvent(Type type, string eventName)
         /// <exception cref="Exception">Thrown if the methods aren't overriden on the target object.</exception>
         public static void ThrowIfMethodsNotOverloaded(string callingTypeName, object targetObject, params string[] methodsToCheck)
         {
-            var missingMethod = methodsToCheck
+            var (methodName, methodImplementation) = methodsToCheck
                 .Select(x =>
                 {
-                    IEnumerable<MethodInfo> methods = targetObject.GetType().GetTypeInfo().DeclaredMethods;
+                    var methods = targetObject.GetType().GetTypeInfo().DeclaredMethods;
                     return (methodName: x, methodImplementation: methods.FirstOrDefault(y => y.Name == x));
                 })
                 .FirstOrDefault(x => x.methodImplementation == null);
 
-            if (missingMethod.methodName != default)
+            if (methodName != default)
             {
-                throw new Exception($"Your class must implement {missingMethod.methodName} and call {callingTypeName}.{missingMethod.methodName}");
+                throw new Exception($"Your class must implement {methodName} and call {callingTypeName}.{methodName}");
             }
         }
 
@@ -438,15 +397,16 @@ public static bool IsStatic(this PropertyInfo item)
             return method.IsStatic;
         }
 
-        [SuppressMessage("Microsoft.Performance", "CA1801", Justification = "TViewModel used to help generic calling.")]
-        internal static IObservable<object> ViewModelWhenAnyValue<TView, TViewModel>(TViewModel? viewModel, TView view, Expression expression)
+#pragma warning disable IDE0060 // Remove unused parameter
+#pragma warning disable RCS1163 // Unused parameter.
+        internal static IObservable<object> ViewModelWhenAnyValue<TView, TViewModel>(TViewModel? viewModel, TView view, Expression? expression)
+#pragma warning restore RCS1163 // Unused parameter.
+#pragma warning restore IDE0060 // Remove unused parameter
             where TView : class, IViewFor
-            where TViewModel : class
-        {
-            return view.WhenAnyValue(x => x.ViewModel)
-                .Where(x => x != null)
-                .Select(x => ((TViewModel)x!).WhenAnyDynamic(expression, y => y.Value))
-                .Switch();
-        }
+            where TViewModel : class =>
+                    view.WhenAnyValue(x => x.ViewModel)
+                        .Where(x => x != null)
+                        .Select(x => ((TViewModel?)x).WhenAnyDynamic(expression, y => y.Value))
+                        .Switch()!;
     }
 }
diff --git a/src/ReactiveUI/Interfaces/IObservedChange.cs b/src/ReactiveUI/Interfaces/IObservedChange.cs
index 35339bf588..23ce14290b 100644
--- a/src/ReactiveUI/Interfaces/IObservedChange.cs
+++ b/src/ReactiveUI/Interfaces/IObservedChange.cs
@@ -24,7 +24,7 @@ public interface IObservedChange<out TSender, out TValue>
         /// <summary>
         /// Gets the expression of the member that has changed on Sender.
         /// </summary>
-        Expression Expression { get; }
+        Expression? Expression { get; }
 
         /// <summary>
         /// Gets the value of the property that has changed. IMPORTANT NOTE: This
diff --git a/src/ReactiveUI/Interfaces/ObservedChange.cs b/src/ReactiveUI/Interfaces/ObservedChange.cs
index e5ef249f16..3d89b2f99e 100644
--- a/src/ReactiveUI/Interfaces/ObservedChange.cs
+++ b/src/ReactiveUI/Interfaces/ObservedChange.cs
@@ -20,7 +20,7 @@ public class ObservedChange<TSender, TValue> : IObservedChange<TSender, TValue>
         /// <param name="sender">The sender.</param>
         /// <param name="expression">Expression describing the member.</param>
         /// <param name="value">The value.</param>
-        public ObservedChange(TSender sender, Expression expression, TValue value)
+        public ObservedChange(TSender sender, Expression? expression, TValue value)
         {
             Sender = sender;
             Expression = expression;
@@ -31,7 +31,7 @@ public ObservedChange(TSender sender, Expression expression, TValue value)
         public TSender Sender { get; }
 
         /// <inheritdoc/>
-        public Expression Expression { get; }
+        public Expression? Expression { get; }
 
         /// <inheritdoc/>
         public TValue Value { get; }
diff --git a/src/ReactiveUI/Mixins/AutoPersistHelper.cs b/src/ReactiveUI/Mixins/AutoPersistHelper.cs
index 69e0bbd0e5..96a62c7007 100644
--- a/src/ReactiveUI/Mixins/AutoPersistHelper.cs
+++ b/src/ReactiveUI/Mixins/AutoPersistHelper.cs
@@ -94,7 +94,7 @@ public static IDisposable AutoPersist<T, TDontCare>(this T @this, Func<T, IObser
                 throw new ArgumentException("AutoPersist can only be applied to objects with [DataContract]");
             }
 
-            Dictionary<string, bool> persistableProperties = persistablePropertiesCache.Get(@this.GetType());
+            var persistableProperties = persistablePropertiesCache.Get(@this.GetType());
 
             var saveHint = @this.GetChangedObservable().Where(x => x.PropertyName is not null && persistableProperties.ContainsKey(x.PropertyName)).Select(_ => Unit.Default).Merge(manualSaveSignal.Select(_ => Unit.Default));
 
diff --git a/src/ReactiveUI/Mixins/ExpressionMixins.cs b/src/ReactiveUI/Mixins/ExpressionMixins.cs
index ae43a4f737..f3741d6895 100644
--- a/src/ReactiveUI/Mixins/ExpressionMixins.cs
+++ b/src/ReactiveUI/Mixins/ExpressionMixins.cs
@@ -27,7 +27,7 @@ public static class ExpressionMixins
         public static IEnumerable<Expression> GetExpressionChain(this Expression expression)
         {
             var expressions = new List<Expression>();
-            Expression? node = expression;
+            var node = expression;
 
             while (node is not null && node.NodeType != ExpressionType.Parameter)
             {
diff --git a/src/ReactiveUI/Mixins/ObservedChangedMixin.cs b/src/ReactiveUI/Mixins/ObservedChangedMixin.cs
index 72d4e906b4..127608c277 100644
--- a/src/ReactiveUI/Mixins/ObservedChangedMixin.cs
+++ b/src/ReactiveUI/Mixins/ObservedChangedMixin.cs
@@ -23,15 +23,10 @@ public static class ObservedChangedMixin
         /// <returns>
         /// The name of the property which has changed.
         /// </returns>
-        public static string GetPropertyName<TSender, TValue>(this IObservedChange<TSender, TValue> item)
-        {
-            if (item is null)
-            {
-                throw new ArgumentNullException(nameof(item));
-            }
-
-            return Reflection.ExpressionToPropertyNames(item.Expression);
-        }
+        public static string GetPropertyName<TSender, TValue>(this IObservedChange<TSender, TValue> item) =>
+            item is null
+            ? throw new ArgumentNullException(nameof(item))
+            : Reflection.ExpressionToPropertyNames(item.Expression);
 
         /// <summary>
         /// Returns the current value of a property given a notification that
@@ -45,20 +40,12 @@ public static string GetPropertyName<TSender, TValue>(this IObservedChange<TSend
         /// <returns>
         /// The current value of the property.
         /// </returns>
-        public static TValue GetValue<TSender, TValue>(this IObservedChange<TSender, TValue> item)
-        {
-            if (item is null)
-            {
-                throw new ArgumentNullException(nameof(item));
-            }
-
-            if (!item.TryGetValue(out var returnValue))
-            {
-                throw new Exception($"One of the properties in the expression '{item.GetPropertyName()}' was null");
-            }
-
-            return returnValue;
-        }
+        public static TValue GetValue<TSender, TValue>(this IObservedChange<TSender, TValue> item) =>
+            item is null
+                ? throw new ArgumentNullException(nameof(item))
+                : !item.TryGetValue(out var returnValue)
+                ? throw new Exception($"One of the properties in the expression '{item.GetPropertyName()}' was null")
+                : returnValue;
 
         /// <summary>
         /// Returns the current value of a property given a notification that
@@ -72,20 +59,8 @@ public static TValue GetValue<TSender, TValue>(this IObservedChange<TSender, TVa
         /// <returns>
         /// The current value of the property.
         /// </returns>
-        public static TValue? GetValueOrDefault<TSender, TValue>(this IObservedChange<TSender, TValue> item)
-        {
-            if (item is null)
-            {
-                throw new ArgumentNullException(nameof(item));
-            }
-
-            if (!item.TryGetValue(out var returnValue))
-            {
-                return default;
-            }
-
-            return returnValue;
-        }
+        public static TValue? GetValueOrDefault<TSender, TValue>(this IObservedChange<TSender, TValue> item) =>
+            item is null ? throw new ArgumentNullException(nameof(item)) : !item.TryGetValue(out var returnValue) ? default : returnValue;
 
         /// <summary>
         /// Given a stream of notification changes, this method will convert
@@ -128,7 +103,7 @@ internal static bool TryGetValue<TSender, TValue>(this IObservedChange<TSender,
                 return true;
             }
 
-            return Reflection.TryGetValueForPropertyChain(out changeValue, item.Sender, item.Expression.GetExpressionChain());
+            return Reflection.TryGetValueForPropertyChain(out changeValue, item.Sender, item.Expression!.GetExpressionChain());
         }
 
         /// <summary>
diff --git a/src/ReactiveUI/Mixins/ReactiveNotifyPropertyChangedMixin.cs b/src/ReactiveUI/Mixins/ReactiveNotifyPropertyChangedMixin.cs
index aa12e14933..12612bd3fb 100644
--- a/src/ReactiveUI/Mixins/ReactiveNotifyPropertyChangedMixin.cs
+++ b/src/ReactiveUI/Mixins/ReactiveNotifyPropertyChangedMixin.cs
@@ -25,7 +25,7 @@ public static class ReactiveNotifyPropertyChangedMixin
                     return Locator.Current.GetServices<ICreatesObservableForProperty>()
                                   .Aggregate((score: 0, binding: (ICreatesObservableForProperty?)null), (acc, x) =>
                                   {
-                                      int score = x.GetAffinityForObject(t.senderType, t.propertyName, t.beforeChange);
+                                      var score = x.GetAffinityForObject(t.senderType, t.propertyName, t.beforeChange);
                                       return score > acc.score ? (score, x) : acc;
                                   }).binding;
                 }, RxApp.BigCacheLimit);
@@ -50,9 +50,9 @@ public static class ReactiveNotifyPropertyChangedMixin
         /// with the initial value.</param>
         /// <returns>An Observable representing the property change
         /// notifications for the given property.</returns>
-        public static IObservable<IObservedChange<TSender, TValue>> ObservableForProperty<TSender, TValue>(
-                this TSender item,
-                Expression<Func<TSender, TValue>> property,
+        public static IObservable<IObservedChange<TSender, TValue?>> ObservableForProperty<TSender, TValue>(
+                this TSender? item,
+                Expression<Func<TSender, TValue?>> property,
                 bool beforeChange = false,
                 bool skipInitial = true)
         {
@@ -81,7 +81,7 @@ public static IObservable<IObservedChange<TSender, TValue>> ObservableForPropert
              *  Resubscribe to new Baz, publish to Subject
              */
 
-            return SubscribeToExpressionChain<TSender, TValue>(
+            return SubscribeToExpressionChain<TSender, TValue?>(
                 item,
                 property.Body,
                 beforeChange,
@@ -107,9 +107,9 @@ public static IObservable<IObservedChange<TSender, TValue>> ObservableForPropert
         /// <returns>An Observable representing the property change
         /// notifications for the given property.</returns>
         public static IObservable<TRet> ObservableForProperty<TSender, TValue, TRet>(
-                this TSender item,
-                Expression<Func<TSender, TValue>> property,
-                Func<TValue, TRet> selector,
+                this TSender? item,
+                Expression<Func<TSender, TValue?>> property,
+                Func<TValue?, TRet> selector,
                 bool beforeChange = false)
             where TSender : class
         {
@@ -136,8 +136,8 @@ public static IObservable<TRet> ObservableForProperty<TSender, TValue, TRet>(
         /// <returns>A observable which notifies about observed changes.</returns>
         /// <exception cref="InvalidCastException">If we cannot cast from the target value from the specified last property.</exception>
         public static IObservable<IObservedChange<TSender, TValue>> SubscribeToExpressionChain<TSender, TValue>(
-            this TSender source,
-            Expression expression,
+            this TSender? source,
+            Expression? expression,
             bool beforeChange = false,
             bool skipInitial = true,
             bool suppressWarnings = false)
@@ -150,7 +150,7 @@ public static IObservable<IObservedChange<TSender, TValue>> SubscribeToExpressio
             IObservable<IObservedChange<object?, object?>> notifier =
                 Observable.Return(new ObservedChange<object?, object?>(null, null!, source));
 
-            IEnumerable<Expression> chain = Reflection.Rewrite(expression).GetExpressionChain();
+            var chain = Reflection.Rewrite(expression).GetExpressionChain();
             notifier = chain.Aggregate(notifier, (n, expr) => n
                 .Select(y => NestedObservedChanges(expr, y, beforeChange, suppressWarnings))
                 .Switch());
diff --git a/src/ReactiveUI/ObservableForProperty/OAPHCreationHelperMixin.cs b/src/ReactiveUI/ObservableForProperty/OAPHCreationHelperMixin.cs
index ccd95847a4..f18c168869 100644
--- a/src/ReactiveUI/ObservableForProperty/OAPHCreationHelperMixin.cs
+++ b/src/ReactiveUI/ObservableForProperty/OAPHCreationHelperMixin.cs
@@ -643,7 +643,7 @@ private static ObservableAsPropertyHelper<TRet> ObservableToProperty<TObj, TRet>
                 throw new ArgumentNullException(nameof(property));
             }
 
-            Expression expression = Reflection.Rewrite(property.Body);
+            var expression = Reflection.Rewrite(property.Body);
 
             var parent = expression.GetParent();
 
@@ -664,7 +664,7 @@ private static ObservableAsPropertyHelper<TRet> ObservableToProperty<TObj, TRet>
                 throw new ArgumentException("The property expression does not point towards a valid member.", nameof(property));
             }
 
-            string name = memberInfo.Name;
+            var name = memberInfo.Name;
             if (expression is IndexExpression)
             {
                 name += "[]";
@@ -702,7 +702,7 @@ private static ObservableAsPropertyHelper<TRet> ObservableToProperty<TObj, TRet>
                 throw new ArgumentNullException(nameof(property));
             }
 
-            Expression expression = Reflection.Rewrite(property.Body);
+            var expression = Reflection.Rewrite(property.Body);
 
             var parent = expression.GetParent();
 
@@ -723,7 +723,7 @@ private static ObservableAsPropertyHelper<TRet> ObservableToProperty<TObj, TRet>
                 throw new ArgumentException("The property expression does not point towards a valid member.", nameof(property));
             }
 
-            string name = memberInfo.Name;
+            var name = memberInfo.Name;
             if (expression is IndexExpression)
             {
                 name += "[]";
diff --git a/src/ReactiveUI/Platforms/android/AndroidCommandBinders.cs b/src/ReactiveUI/Platforms/android/AndroidCommandBinders.cs
index 8a9d631f71..02a7872b81 100644
--- a/src/ReactiveUI/Platforms/android/AndroidCommandBinders.cs
+++ b/src/ReactiveUI/Platforms/android/AndroidCommandBinders.cs
@@ -21,7 +21,7 @@ public class AndroidCommandBinders : FlexibleCommandBinder
         /// </summary>
         public AndroidCommandBinders()
         {
-            Type view = typeof(View);
+            var view = typeof(View);
             Register(view, 9, (cmd, t, cp) => ForEvent(cmd, t, cp, "Click", view.GetRuntimeProperty("Enabled")));
         }
 
diff --git a/src/ReactiveUI/Platforms/android/HandlerScheduler.cs b/src/ReactiveUI/Platforms/android/HandlerScheduler.cs
index d7f508e16d..058d86c5e4 100644
--- a/src/ReactiveUI/Platforms/android/HandlerScheduler.cs
+++ b/src/ReactiveUI/Platforms/android/HandlerScheduler.cs
@@ -53,7 +53,7 @@ public HandlerScheduler(Handler handler, long? threadIdAssociatedWithHandler)
         /// <inheritdoc/>
         public IDisposable Schedule<TState>(TState state, Func<IScheduler, TState, IDisposable> action)
         {
-            bool isCancelled = false;
+            var isCancelled = false;
             var innerDisp = new SerialDisposable() { Disposable = Disposable.Empty };
 
             _handler.Post(() =>
@@ -74,7 +74,7 @@ public IDisposable Schedule<TState>(TState state, Func<IScheduler, TState, IDisp
         /// <inheritdoc/>
         public IDisposable Schedule<TState>(TState state, TimeSpan dueTime, Func<IScheduler, TState, IDisposable> action)
         {
-            bool isCancelled = false;
+            var isCancelled = false;
             var innerDisp = new SerialDisposable() { Disposable = Disposable.Empty };
 
             _handler.PostDelayed(
diff --git a/src/ReactiveUI/Platforms/apple-common/KVOObservableForProperty.cs b/src/ReactiveUI/Platforms/apple-common/KVOObservableForProperty.cs
index be6d1e303c..534a15308b 100644
--- a/src/ReactiveUI/Platforms/apple-common/KVOObservableForProperty.cs
+++ b/src/ReactiveUI/Platforms/apple-common/KVOObservableForProperty.cs
@@ -94,7 +94,7 @@ static KVOObservableForProperty()
 
         private static string FindCocoaNameFromNetName(Type senderType, string propertyName)
         {
-            bool propIsBoolean = false;
+            var propIsBoolean = false;
 
             var pi = senderType.GetTypeInfo().DeclaredProperties.FirstOrDefault(x => !x.IsStatic());
             if (pi is null)
diff --git a/src/ReactiveUI/Platforms/apple-common/NSRunloopScheduler.cs b/src/ReactiveUI/Platforms/apple-common/NSRunloopScheduler.cs
index 7740c91599..7c211bd7b9 100644
--- a/src/ReactiveUI/Platforms/apple-common/NSRunloopScheduler.cs
+++ b/src/ReactiveUI/Platforms/apple-common/NSRunloopScheduler.cs
@@ -52,7 +52,7 @@ public IDisposable Schedule<TState>(TState state, DateTimeOffset dueTime, Func<I
         public IDisposable Schedule<TState>(TState state, TimeSpan dueTime, Func<IScheduler, TState, IDisposable> action)
         {
             var innerDisp = Disposable.Empty;
-            bool isCancelled = false;
+            var isCancelled = false;
 
             var timer = NSTimer.CreateScheduledTimer(dueTime, _ =>
             {
diff --git a/src/ReactiveUI/Platforms/apple-common/ObservableForPropertyBase.cs b/src/ReactiveUI/Platforms/apple-common/ObservableForPropertyBase.cs
index 2538db8f45..01bd2ae74f 100644
--- a/src/ReactiveUI/Platforms/apple-common/ObservableForPropertyBase.cs
+++ b/src/ReactiveUI/Platforms/apple-common/ObservableForPropertyBase.cs
@@ -150,7 +150,7 @@ public int GetAffinityForObject(Type type, string propertyName, bool beforeChang
         /// <param name="createObservable">Create observable.</param>
         protected void Register(Type type, string property, int affinity, Func<NSObject, Expression, IObservable<IObservedChange<object, object?>>> createObservable)
         {
-            if (!_config.TryGetValue(type, out Dictionary<string, ObservablePropertyInfo> typeProperties))
+            if (!_config.TryGetValue(type, out var typeProperties))
             {
                 typeProperties = new Dictionary<string, ObservablePropertyInfo>();
                 _config[type] = typeProperties;
diff --git a/src/ReactiveUI/Platforms/apple-common/TargetActionCommandBinder.cs b/src/ReactiveUI/Platforms/apple-common/TargetActionCommandBinder.cs
index bdbf7ef1a3..2c1331089c 100644
--- a/src/ReactiveUI/Platforms/apple-common/TargetActionCommandBinder.cs
+++ b/src/ReactiveUI/Platforms/apple-common/TargetActionCommandBinder.cs
@@ -99,7 +99,7 @@ public IDisposable BindCommandToObject(ICommand command, object target, IObserva
             targetSetter?.Invoke(target, ctlDelegate, null);
             var actionDisp = Disposable.Create(() => targetSetter?.Invoke(target, null, null));
 
-            Action<object, object, object[]?>? enabledSetter = Reflection.GetValueSetterForProperty(target.GetType().GetRuntimeProperty("Enabled"));
+            var enabledSetter = Reflection.GetValueSetterForProperty(target.GetType().GetRuntimeProperty("Enabled"));
             if (enabledSetter is null)
             {
                 return actionDisp;
diff --git a/src/ReactiveUI/Platforms/apple-common/ViewModelViewHost.cs b/src/ReactiveUI/Platforms/apple-common/ViewModelViewHost.cs
index a15139bab4..b8b656033e 100644
--- a/src/ReactiveUI/Platforms/apple-common/ViewModelViewHost.cs
+++ b/src/ReactiveUI/Platforms/apple-common/ViewModelViewHost.cs
@@ -22,8 +22,6 @@ namespace ReactiveUI
     /// A control which will use Splat dependency injection to determine the View
     /// to show. It uses.
     /// </summary>
-    [SuppressMessage("StyleCop.CSharp.MaintainabilityRules", "SA1402:FileMayOnlyContainASingleType", Justification = "Classes with the same class names within.")]
-    [SuppressMessage("Design", "CA1010: Implement generic IEnumerable", Justification = "UI Kit exposes IEnumerable")]
     public class ViewModelViewHost : ReactiveViewController
     {
         private readonly SerialDisposable _currentView;
@@ -40,7 +38,7 @@ public ViewModelViewHost()
         {
             _currentView = new SerialDisposable();
             _viewContract = this
-                .WhenAnyObservable(x => x.ViewContractObservable!)
+                .WhenAnyObservable(x => x.ViewContractObservable)
                 .ToProperty(this, x => x.ViewContract, initialValue: null, scheduler: RxApp.MainThreadScheduler);
 
             Initialize();
@@ -174,16 +172,14 @@ private static void Disown(NSViewController child)
 
         private void Initialize()
         {
-            var viewChange = Observable
+            var viewChange = this.WhenAnyValue(x => x.ViewModel)
                 .CombineLatest(
-                    this.WhenAnyValue(x => x.ViewModel),
-                    this.WhenAnyObservable(x => x.ViewContractObservable!).StartWith((string?)null),
+                    this.WhenAnyObservable(x => x.ViewContractObservable).StartWith((string?)null),
                     (vm, contract) => new { ViewModel = vm, Contract = contract })
                 .Where(x => x.ViewModel is not null);
 
-            var defaultViewChange = Observable
+            var defaultViewChange = this.WhenAnyValue(x => x.ViewModel)
                 .CombineLatest(
-                    this.WhenAnyValue(x => x.ViewModel),
                     this.WhenAnyValue(x => x.DefaultContent),
                     (vm, defaultContent) => new { ViewModel = vm, DefaultContent = defaultContent })
                 .Where(x => x.ViewModel is null && x.DefaultContent is not null)
@@ -210,20 +206,25 @@ private void Initialize()
                             throw new Exception(message);
                         }
 
+#pragma warning disable RCS1221 // Use pattern matching instead of combination of 'as' operator and null check.
                         var viewController = view as NSViewController;
+#pragma warning restore RCS1221 // Use pattern matching instead of combination of 'as' operator and null check.
 
                         if (viewController is null)
                         {
+                            //// TODO: As viewController = NULL at this point this excetion will never show the FullName, find fixed text to replace this with.
+
                             throw new Exception($"Resolved view type '{viewController?.GetType().FullName}' is not a '{typeof(NSViewController).FullName}'.");
                         }
 
                         view.ViewModel = x.ViewModel;
                         Adopt(this, viewController);
 
-                        var disposables = new CompositeDisposable();
-                        disposables.Add(viewController);
-                        disposables.Add(Disposable.Create(() => Disown(viewController)));
-                        _currentView.Disposable = disposables;
+                        _currentView.Disposable = (CompositeDisposable?)new()
+                        {
+                            viewController,
+                            Disposable.Create(() => Disown(viewController))
+                        };
                     });
 
             defaultViewChange
diff --git a/src/ReactiveUI/Platforms/tizen/EcoreMainloopScheduler.cs b/src/ReactiveUI/Platforms/tizen/EcoreMainloopScheduler.cs
index 28c37118ab..e1b9acd832 100644
--- a/src/ReactiveUI/Platforms/tizen/EcoreMainloopScheduler.cs
+++ b/src/ReactiveUI/Platforms/tizen/EcoreMainloopScheduler.cs
@@ -32,7 +32,7 @@ public IDisposable Schedule<TState>(TState state, Func<IScheduler, TState, IDisp
         public IDisposable Schedule<TState>(TState state, TimeSpan dueTime, Func<IScheduler, TState, IDisposable> action)
         {
             var innerDisp = Disposable.Empty;
-            bool isCancelled = false;
+            var isCancelled = false;
 
             var timer = EcoreMainloop.AddTimer(dueTime.TotalSeconds, () =>
             {
diff --git a/src/ReactiveUI/Platforms/uikit-common/CommonReactiveSource.cs b/src/ReactiveUI/Platforms/uikit-common/CommonReactiveSource.cs
index b323216287..8b91526789 100644
--- a/src/ReactiveUI/Platforms/uikit-common/CommonReactiveSource.cs
+++ b/src/ReactiveUI/Platforms/uikit-common/CommonReactiveSource.cs
@@ -146,7 +146,7 @@ private static IEnumerable<Update> GetUpdatesForEvent(PendingChange pendingChang
                     // When item at index 1 is removed item at index 2 is now at index 1 and so on down the line.
                     return Enumerable
                         .Range(pendingChange.OldStartingIndex, pendingChange.OldItems is null ? 1 : pendingChange.OldItems.Count)
-                        .Select(x => Update.CreateDelete(pendingChange.OldStartingIndex));
+                        .Select(_ => Update.CreateDelete(pendingChange.OldStartingIndex));
                 case NotifyCollectionChangedAction.Move:
                     return Enumerable
                         .Range(pendingChange.OldStartingIndex, pendingChange.OldItems is null ? 1 : pendingChange.OldItems.Count)
@@ -172,7 +172,7 @@ private void SectionInfoChanging()
             _sectionInfoDisposable.Disposable = null;
         }
 
-        private void SectionInfoChanged(IReadOnlyList<TSectionInfo> sectionInfo)
+        private void SectionInfoChanged(IReadOnlyList<TSectionInfo>? sectionInfo)
         {
             VerifyOnMainThread();
 
@@ -236,10 +236,9 @@ private void SubscribeToSectionInfoChanges(int sectionInfoId, IReadOnlyList<TSec
                         .Do(y => this.Log().Debug(CultureInfo.InvariantCulture, "[#{0}] IsReloadingData = {1}", sectionInfoId, y))
                         .Publish();
 
-                    var anySectionChanged = Observable
-                        .Merge(
-                            sectionInfo
-                            .Select((y, index) => y.Collection!.ObserveCollectionChanges().Select(z => new { Section = index, Change = z })))
+                    var anySectionChanged = sectionInfo
+                            .Select((y, index) => y.Collection!.ObserveCollectionChanges().Select(z => new { Section = index, Change = z }))
+                        .Merge()
                         .Publish();
 
                     // since reloads are applied asynchronously, it is possible for data to change whilst the reload is occurring
@@ -269,7 +268,7 @@ private void SubscribeToSectionInfoChanges(int sectionInfoId, IReadOnlyList<TSec
                             anySectionChanged,
                             _ => isReloading,
                             _ => Observable<Unit>.Empty,
-                            (reloading, changeDetails) => new { Change = changeDetails.Change, Section = changeDetails.Section })
+                            (_, changeDetails) => (changeDetails.Change, changeDetails.Section))
                         .Subscribe(
                             y =>
                         {
@@ -336,18 +335,18 @@ private void ApplyPendingChanges(int sectionInfoId)
                         {
                             this.Log().Debug(CultureInfo.InvariantCulture, "[#{0}] The pending changes (in order received) are:", sectionInfoId);
 
-                            foreach (var pendingSectionChange in _pendingChanges)
+                            foreach (var (section, pendingChange) in _pendingChanges)
                             {
                                 this.Log().Debug(
                                     CultureInfo.InvariantCulture,
                                     "[#{0}] Section {1}: Action = {2}, OldStartingIndex = {3}, NewStartingIndex = {4}, OldItems.Count = {5}, NewItems.Count = {6}",
                                     sectionInfoId,
-                                    pendingSectionChange.section,
-                                    pendingSectionChange.pendingChange.Action,
-                                    pendingSectionChange.pendingChange.OldStartingIndex,
-                                    pendingSectionChange.pendingChange.NewStartingIndex,
-                                    pendingSectionChange.pendingChange.OldItems is null ? "null" : pendingSectionChange.pendingChange.OldItems.Count.ToString(CultureInfo.InvariantCulture),
-                                    pendingSectionChange.pendingChange.NewItems is null ? "null" : pendingSectionChange.pendingChange.NewItems.Count.ToString(CultureInfo.InvariantCulture));
+                                    section,
+                                    pendingChange.Action,
+                                    pendingChange.OldStartingIndex,
+                                    pendingChange.NewStartingIndex,
+                                    pendingChange.OldItems is null ? "null" : pendingChange.OldItems.Count.ToString(CultureInfo.InvariantCulture),
+                                    pendingChange.NewItems is null ? "null" : pendingChange.NewItems.Count.ToString(CultureInfo.InvariantCulture));
                             }
                         }
 
diff --git a/src/ReactiveUI/Platforms/uikit-common/FlexibleCommandBinder.cs b/src/ReactiveUI/Platforms/uikit-common/FlexibleCommandBinder.cs
index a0071f6d06..e5083af346 100644
--- a/src/ReactiveUI/Platforms/uikit-common/FlexibleCommandBinder.cs
+++ b/src/ReactiveUI/Platforms/uikit-common/FlexibleCommandBinder.cs
@@ -149,7 +149,7 @@ protected static IDisposable ForTargetAction(ICommand command, object target, IO
 
             object? latestParam = null;
 
-            IDisposable actionDisposable = Disposable.Empty;
+            var actionDisposable = Disposable.Empty;
 
             if (target is UIControl ctl)
             {
diff --git a/src/ReactiveUI/Platforms/uikit-common/RoutedViewHost.cs b/src/ReactiveUI/Platforms/uikit-common/RoutedViewHost.cs
index d2785853c7..b1943d8be1 100644
--- a/src/ReactiveUI/Platforms/uikit-common/RoutedViewHost.cs
+++ b/src/ReactiveUI/Platforms/uikit-common/RoutedViewHost.cs
@@ -60,7 +60,7 @@ public RoutedViewHost()
                                 if (view is not null)
                                 {
                                     _titleUpdater.Disposable = Router.GetCurrentViewModel()
-                                        .WhenAnyValue(y => y!.UrlPathSegment)
+                                        .WhenAnyValue(y => y.UrlPathSegment)
                                         .Subscribe(y => view.NavigationItem.Title = y);
                                 }
                             }
@@ -86,7 +86,7 @@ public RoutedViewHost()
                             if (x?.View is not null)
                             {
                                 _titleUpdater.Disposable = Router.GetCurrentViewModel()
-                                    .WhenAnyValue(y => y!.UrlPathSegment)
+                                    .WhenAnyValue(y => y.UrlPathSegment)
                                     .Subscribe(y => x.View.NavigationItem.Title = y);
                             }
 
@@ -205,12 +205,9 @@ protected override void Dispose(bool disposing)
 
             view.ViewModel = viewModel;
 
-            if (!(view is NSViewController viewController))
-            {
-                throw new Exception($"View type {view.GetType().Name} for view model type {viewModel.GetType().Name} is not a UIViewController");
-            }
-
-            return viewController;
+            return view is not NSViewController viewController
+                ? throw new Exception($"View type {view.GetType().Name} for view model type {viewModel.GetType().Name} is not a UIViewController")
+                : viewController;
         }
     }
 }
diff --git a/src/ReactiveUI/Platforms/windows-common/AutoDataTemplateBindingHook.cs b/src/ReactiveUI/Platforms/windows-common/AutoDataTemplateBindingHook.cs
index 3fb5aaeb29..3eb5e44be3 100644
--- a/src/ReactiveUI/Platforms/windows-common/AutoDataTemplateBindingHook.cs
+++ b/src/ReactiveUI/Platforms/windows-common/AutoDataTemplateBindingHook.cs
@@ -48,7 +48,7 @@ public class AutoDataTemplateBindingHook : IPropertyBindingHook
                  "<xaml:ViewModelViewHost ViewModel=\"{Binding Mode=OneWay}\" VerticalContentAlignment=\"Stretch\" HorizontalContentAlignment=\"Stretch\" IsTabStop=\"False\" />" +
              "</DataTemplate>";
 
-            string? assemblyName = typeof(AutoDataTemplateBindingHook).Assembly.FullName;
+            var assemblyName = typeof(AutoDataTemplateBindingHook).Assembly.FullName;
             assemblyName = assemblyName?.Substring(0, assemblyName.IndexOf(','));
 
             return (DataTemplate)XamlReader.Parse(template.Replace("__ASSEMBLYNAME__", assemblyName));
diff --git a/src/ReactiveUI/ReactiveCommand/ReactiveCommandBase.cs b/src/ReactiveUI/ReactiveCommand/ReactiveCommandBase.cs
index f5354c58fe..74cf2b01f8 100644
--- a/src/ReactiveUI/ReactiveCommand/ReactiveCommandBase.cs
+++ b/src/ReactiveUI/ReactiveCommand/ReactiveCommandBase.cs
@@ -242,7 +242,7 @@ protected virtual void ICommandExecute(object? parameter)
                     $"Command requires parameters of type {typeof(TParam).FullName}, but received parameter of type {parameter.GetType().FullName}.");
             }
 
-            IObservable<TResult> result = parameter is null ? Execute() : Execute((TParam)parameter);
+            var result = parameter is null ? Execute() : Execute((TParam)parameter);
 
             result
                 .Catch(Observable<TResult>.Empty)
diff --git a/src/ReactiveUI/ReactiveCommand/ReactiveCommandMixins.cs b/src/ReactiveUI/ReactiveCommand/ReactiveCommandMixins.cs
index 9ae4601e49..522de9d12a 100644
--- a/src/ReactiveUI/ReactiveCommand/ReactiveCommandMixins.cs
+++ b/src/ReactiveUI/ReactiveCommand/ReactiveCommandMixins.cs
@@ -55,18 +55,13 @@ public static IDisposable InvokeCommand<T>(this IObservable<T> item, ICommand? c
         /// <param name="command">The command to be executed.</param>
         /// <returns>An object that when disposes, disconnects the Observable
         /// from the command.</returns>
-        public static IDisposable InvokeCommand<T, TResult>(this IObservable<T> item, ReactiveCommandBase<T, TResult>? command)
-        {
-            if (command is null)
-            {
-                throw new ArgumentNullException(nameof(command));
-            }
-
-            return WithLatestFromFixed(item, command.CanExecute, (value, canExecute) => new InvokeCommandInfo<ReactiveCommandBase<T, TResult>, T>(command, canExecute, value))
+        public static IDisposable InvokeCommand<T, TResult>(this IObservable<T> item, ReactiveCommandBase<T, TResult>? command) =>
+            command is null
+                ? throw new ArgumentNullException(nameof(command))
+                : WithLatestFromFixed(item, command.CanExecute, (value, canExecute) => new InvokeCommandInfo<ReactiveCommandBase<T, TResult>, T>(command, canExecute, value))
                 .Where(ii => ii.CanExecute)
                 .SelectMany(ii => command.Execute(ii.Value).Catch(Observable<TResult>.Empty))
                 .Subscribe();
-        }
 
         /// <summary>
         /// A utility method that will pipe an Observable to an ICommand (i.e.
@@ -83,7 +78,7 @@ public static IDisposable InvokeCommand<T, TResult>(this IObservable<T> item, Re
         public static IDisposable InvokeCommand<T, TTarget>(this IObservable<T> item, TTarget? target, Expression<Func<TTarget, ICommand?>> commandProperty)
             where TTarget : class
         {
-            var commandObs = target.WhenAnyValue(commandProperty!);
+            var commandObs = target.WhenAnyValue(commandProperty);
             var commandCanExecuteChanged = commandObs
                 .Select(command => command is null ? Observable<ICommand>.Empty : Observable
                     .FromEvent<EventHandler, ICommand>(
@@ -115,7 +110,7 @@ public static IDisposable InvokeCommand<T, TTarget>(this IObservable<T> item, TT
         public static IDisposable InvokeCommand<T, TResult, TTarget>(this IObservable<T> item, TTarget? target, Expression<Func<TTarget, ReactiveCommandBase<T, TResult>?>> commandProperty)
             where TTarget : class
         {
-            var command = target.WhenAnyValue(commandProperty!);
+            var command = target.WhenAnyValue(commandProperty);
             var invocationInfo = command
                 .Select(cmd => cmd is null ?
                                    Observable<InvokeCommandInfo<ReactiveCommandBase<T, TResult>, T>>.Empty :
diff --git a/src/ReactiveUI/ReactiveObject/IReactiveObjectExtensions.cs b/src/ReactiveUI/ReactiveObject/IReactiveObjectExtensions.cs
index 02c3c0ad21..ca33ae1fe5 100644
--- a/src/ReactiveUI/ReactiveObject/IReactiveObjectExtensions.cs
+++ b/src/ReactiveUI/ReactiveObject/IReactiveObjectExtensions.cs
@@ -398,7 +398,7 @@ private static IEnumerable<TEventArgs> DistinctEvents<TEventArgs>(IList<TEventAr
                 var seen = new HashSet<string>();
                 var uniqueEvents = new Stack<TEventArgs>(events.Count);
 
-                for (int i = events.Count - 1; i >= 0; i--)
+                for (var i = events.Count - 1; i >= 0; i--)
                 {
                     var propertyName = events[i].PropertyName;
                     if (propertyName is not null && seen.Add(propertyName))
diff --git a/src/ReactiveUI/Routing/MessageBus.cs b/src/ReactiveUI/Routing/MessageBus.cs
index 576d9027a8..34a2ae7a9e 100644
--- a/src/ReactiveUI/Routing/MessageBus.cs
+++ b/src/ReactiveUI/Routing/MessageBus.cs
@@ -92,7 +92,7 @@ public IObservable<T> ListenIncludeLatest<T>(string? contract = null)
         /// <returns>True if messages have been posted for this message Type.</returns>
         public bool IsRegistered(Type type, string? contract = null)
         {
-            bool ret = false;
+            var ret = false;
             WithMessageBus(type, contract, (mb, item) => { ret = mb.ContainsKey(item) && mb[item].IsAlive; });
 
             return ret;
diff --git a/src/ReactiveUI/VariadicTemplates.cs b/src/ReactiveUI/VariadicTemplates.cs
index c5ee2ec4d7..c8f935b63d 100644
--- a/src/ReactiveUI/VariadicTemplates.cs
+++ b/src/ReactiveUI/VariadicTemplates.cs
@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 //------------------------------------------------------------------------------
 // <auto-generated>
 //    This code was generated from a template.
@@ -31,15 +33,15 @@ public static class WhenAnyMixin
         /// </summary>
         /// <param name="sender">The object where the property chain starts.</param>
         /// <param name="property1">The first property chain to reference. This will be a expression pointing to a end property or field.</param>
-        public static IObservable<TRet> WhenAnyValue<TSender, TRet>(
-            this TSender sender,
-            Expression<Func<TSender, TRet>> property1)
+        public static IObservable<TRet?> WhenAnyValue<TSender, TRet>(
+            this TSender? sender,
+            Expression<Func<TSender, TRet?>> property1)
         {
-            return sender.WhenAny(property1, (IObservedChange<TSender, TRet> c1) => c1.Value);
+            return sender.WhenAny(property1, (IObservedChange<TSender, TRet?> c1) => c1.Value);
         }
 
-
-
+                                                                        
+        
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -50,10 +52,10 @@ public static IObservable<TRet> WhenAnyValue<TSender, TRet>(
         /// <param name="sender">The object where the property chain starts.</param>
         /// <param name="property1">The 1 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Func<T1, TRet> selector)
+        public static IObservable<TRet?> WhenAnyValue<TSender, TRet, T1>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Func<T1?, TRet> selector)
         {
             return sender.WhenAny(property1,
                                 (c1) =>
@@ -70,13 +72,13 @@ public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1>(
         /// <param name="sender">The object where the property chain starts.</param>
         /// <param name="property1">The 1 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAny<TSender, TRet, T1>(
-                this TSender sender,
-                            Expression<Func<TSender, T1>> property1,
-                            Func<IObservedChange<TSender, T1>, TRet> selector)
+        public static IObservable<TRet?> WhenAny<TSender, TRet, T1>(
+                this TSender? sender,
+                            Expression<Func<TSender, T1?>> property1,
+                            Func<IObservedChange<TSender, T1?>, TRet?> selector)
         {
-            return sender.ObservableForProperty(property1, false, false).Select(selector);
-        }
+                            return sender.ObservableForProperty(property1, false, false).Select(selector);
+                    }
 
 
         /// <summary>
@@ -89,15 +91,15 @@ public static IObservable<TRet> WhenAny<TSender, TRet, T1>(
         /// <param name="sender">The object where the property chain starts.</param>
         /// <param name="property1">The 1 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
-                this TSender sender,
-                            Expression property1,
-                            Func<IObservedChange<TSender, object>, TRet> selector)
-        {
-            return ReactiveNotifyPropertyChangedMixin
-    .SubscribeToExpressionChain<TSender, object>(sender, property1, false, false).Select(selector);
-        }
-
+        public static IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(
+                this TSender? sender,
+                            Expression? property1,
+                            Func<IObservedChange<TSender?, object?>, TRet?> selector)
+        {
+                            return ReactiveNotifyPropertyChangedMixin
+                    .SubscribeToExpressionChain<TSender,object?>(sender, property1, false, false).Select(selector);
+                    }
+                                                                    
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -108,17 +110,17 @@ public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
         /// <param name="sender">The object where the property chain starts.</param>
         /// <param name="property1">The 1 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property2">The 2 property chain to reference. This will be a expression pointing to a end property or field.</param>
-        public static IObservable<(T1, T2)> WhenAnyValue<TSender, T1, T2>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2
+        public static IObservable<(T1?,T2?)> WhenAnyValue<TSender, T1,T2>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2
             )
         {
             return sender.WhenAny(property1, property2,
                                 (c1, c2) =>
                                     (c1.Value, c2.Value));
         }
-
+        
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -130,11 +132,11 @@ Expression<Func<TSender, T2>> property2
         /// <param name="property1">The 1 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property2">The 2 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Func<T1, T2, TRet> selector)
+        public static IObservable<TRet?> WhenAnyValue<TSender, TRet, T1,T2>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Func<T1?,T2?, TRet> selector)
         {
             return sender.WhenAny(property1, property2,
                                 (c1, c2) =>
@@ -152,18 +154,18 @@ public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2>(
         /// <param name="property1">The 1 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property2">The 2 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2>(
-                this TSender sender,
-                            Expression<Func<TSender, T1>> property1,
-                            Expression<Func<TSender, T2>> property2,
-                            Func<IObservedChange<TSender, T1>, IObservedChange<TSender, T2>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        sender.ObservableForProperty(property1, false, false),
-                        sender.ObservableForProperty(property2, false, false),
-                    selector
-);
-        }
+        public static IObservable<TRet?> WhenAny<TSender, TRet, T1,T2>(
+                this TSender? sender,
+                            Expression<Func<TSender, T1?>> property1,
+                            Expression<Func<TSender, T2?>> property2,
+                            Func<IObservedChange<TSender, T1?>, IObservedChange<TSender, T2?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    sender.ObservableForProperty(property1, false, false),
+                                    sender.ObservableForProperty(property2, false, false),
+                                selector
+            );
+                    }
 
 
         /// <summary>
@@ -177,21 +179,21 @@ public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2>(
         /// <param name="property1">The 1 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property2">The 2 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
-                this TSender sender,
-                            Expression property1,
-                            Expression property2,
-                            Func<IObservedChange<TSender, object>, IObservedChange<TSender, object>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property1, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property2, false, false),
-                    selector
-);
-        }
-
+        public static IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(
+                this TSender? sender,
+                            Expression? property1,
+                            Expression? property2,
+                            Func<IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property1, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property2, false, false),
+                                selector
+            );
+                    }
+                                                                    
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -203,18 +205,18 @@ public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
         /// <param name="property1">The 1 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property2">The 2 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property3">The 3 property chain to reference. This will be a expression pointing to a end property or field.</param>
-        public static IObservable<(T1, T2, T3)> WhenAnyValue<TSender, T1, T2, T3>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Expression<Func<TSender, T3>> property3
+        public static IObservable<(T1?,T2?,T3?)> WhenAnyValue<TSender, T1,T2,T3>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Expression<Func<TSender, T3?>> property3
             )
         {
             return sender.WhenAny(property1, property2, property3,
                                 (c1, c2, c3) =>
                                     (c1.Value, c2.Value, c3.Value));
         }
-
+        
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -227,12 +229,12 @@ Expression<Func<TSender, T3>> property3
         /// <param name="property2">The 2 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property3">The 3 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Expression<Func<TSender, T3>> property3,
-                        Func<T1, T2, T3, TRet> selector)
+        public static IObservable<TRet?> WhenAnyValue<TSender, TRet, T1,T2,T3>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Expression<Func<TSender, T3?>> property3,
+                        Func<T1?,T2?,T3?, TRet> selector)
         {
             return sender.WhenAny(property1, property2, property3,
                                 (c1, c2, c3) =>
@@ -251,20 +253,20 @@ public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3>(
         /// <param name="property2">The 2 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property3">The 3 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3>(
-                this TSender sender,
-                            Expression<Func<TSender, T1>> property1,
-                            Expression<Func<TSender, T2>> property2,
-                            Expression<Func<TSender, T3>> property3,
-                            Func<IObservedChange<TSender, T1>, IObservedChange<TSender, T2>, IObservedChange<TSender, T3>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        sender.ObservableForProperty(property1, false, false),
-                        sender.ObservableForProperty(property2, false, false),
-                        sender.ObservableForProperty(property3, false, false),
-                    selector
-);
-        }
+        public static IObservable<TRet?> WhenAny<TSender, TRet, T1,T2,T3>(
+                this TSender? sender,
+                            Expression<Func<TSender, T1?>> property1,
+                            Expression<Func<TSender, T2?>> property2,
+                            Expression<Func<TSender, T3?>> property3,
+                            Func<IObservedChange<TSender, T1?>, IObservedChange<TSender, T2?>, IObservedChange<TSender, T3?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    sender.ObservableForProperty(property1, false, false),
+                                    sender.ObservableForProperty(property2, false, false),
+                                    sender.ObservableForProperty(property3, false, false),
+                                selector
+            );
+                    }
 
 
         /// <summary>
@@ -279,24 +281,24 @@ public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3>(
         /// <param name="property2">The 2 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property3">The 3 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
-                this TSender sender,
-                            Expression property1,
-                            Expression property2,
-                            Expression property3,
-                            Func<IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property1, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property2, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property3, false, false),
-                    selector
-);
-        }
-
+        public static IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(
+                this TSender? sender,
+                            Expression? property1,
+                            Expression? property2,
+                            Expression? property3,
+                            Func<IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property1, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property2, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property3, false, false),
+                                selector
+            );
+                    }
+                                                                    
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -309,19 +311,19 @@ public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
         /// <param name="property2">The 2 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property3">The 3 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property4">The 4 property chain to reference. This will be a expression pointing to a end property or field.</param>
-        public static IObservable<(T1, T2, T3, T4)> WhenAnyValue<TSender, T1, T2, T3, T4>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Expression<Func<TSender, T3>> property3,
-                        Expression<Func<TSender, T4>> property4
+        public static IObservable<(T1?,T2?,T3?,T4?)> WhenAnyValue<TSender, T1,T2,T3,T4>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Expression<Func<TSender, T3?>> property3,
+                        Expression<Func<TSender, T4?>> property4
             )
         {
             return sender.WhenAny(property1, property2, property3, property4,
                                 (c1, c2, c3, c4) =>
                                     (c1.Value, c2.Value, c3.Value, c4.Value));
         }
-
+        
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -335,13 +337,13 @@ Expression<Func<TSender, T4>> property4
         /// <param name="property3">The 3 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property4">The 4 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Expression<Func<TSender, T3>> property3,
-                        Expression<Func<TSender, T4>> property4,
-                        Func<T1, T2, T3, T4, TRet> selector)
+        public static IObservable<TRet?> WhenAnyValue<TSender, TRet, T1,T2,T3,T4>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Expression<Func<TSender, T3?>> property3,
+                        Expression<Func<TSender, T4?>> property4,
+                        Func<T1?,T2?,T3?,T4?, TRet> selector)
         {
             return sender.WhenAny(property1, property2, property3, property4,
                                 (c1, c2, c3, c4) =>
@@ -361,22 +363,22 @@ public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4>(
         /// <param name="property3">The 3 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property4">The 4 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4>(
-                this TSender sender,
-                            Expression<Func<TSender, T1>> property1,
-                            Expression<Func<TSender, T2>> property2,
-                            Expression<Func<TSender, T3>> property3,
-                            Expression<Func<TSender, T4>> property4,
-                            Func<IObservedChange<TSender, T1>, IObservedChange<TSender, T2>, IObservedChange<TSender, T3>, IObservedChange<TSender, T4>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        sender.ObservableForProperty(property1, false, false),
-                        sender.ObservableForProperty(property2, false, false),
-                        sender.ObservableForProperty(property3, false, false),
-                        sender.ObservableForProperty(property4, false, false),
-                    selector
-);
-        }
+        public static IObservable<TRet?> WhenAny<TSender, TRet, T1,T2,T3,T4>(
+                this TSender? sender,
+                            Expression<Func<TSender, T1?>> property1,
+                            Expression<Func<TSender, T2?>> property2,
+                            Expression<Func<TSender, T3?>> property3,
+                            Expression<Func<TSender, T4?>> property4,
+                            Func<IObservedChange<TSender, T1?>, IObservedChange<TSender, T2?>, IObservedChange<TSender, T3?>, IObservedChange<TSender, T4?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    sender.ObservableForProperty(property1, false, false),
+                                    sender.ObservableForProperty(property2, false, false),
+                                    sender.ObservableForProperty(property3, false, false),
+                                    sender.ObservableForProperty(property4, false, false),
+                                selector
+            );
+                    }
 
 
         /// <summary>
@@ -392,27 +394,27 @@ public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4>(
         /// <param name="property3">The 3 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property4">The 4 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
-                this TSender sender,
-                            Expression property1,
-                            Expression property2,
-                            Expression property3,
-                            Expression property4,
-                            Func<IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property1, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property2, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property3, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property4, false, false),
-                    selector
-);
-        }
-
+        public static IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(
+                this TSender? sender,
+                            Expression? property1,
+                            Expression? property2,
+                            Expression? property3,
+                            Expression? property4,
+                            Func<IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property1, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property2, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property3, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property4, false, false),
+                                selector
+            );
+                    }
+                                                                    
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -426,20 +428,20 @@ public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
         /// <param name="property3">The 3 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property4">The 4 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property5">The 5 property chain to reference. This will be a expression pointing to a end property or field.</param>
-        public static IObservable<(T1, T2, T3, T4, T5)> WhenAnyValue<TSender, T1, T2, T3, T4, T5>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Expression<Func<TSender, T3>> property3,
-                        Expression<Func<TSender, T4>> property4,
-                        Expression<Func<TSender, T5>> property5
+        public static IObservable<(T1?,T2?,T3?,T4?,T5?)> WhenAnyValue<TSender, T1,T2,T3,T4,T5>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Expression<Func<TSender, T3?>> property3,
+                        Expression<Func<TSender, T4?>> property4,
+                        Expression<Func<TSender, T5?>> property5
             )
         {
             return sender.WhenAny(property1, property2, property3, property4, property5,
                                 (c1, c2, c3, c4, c5) =>
                                     (c1.Value, c2.Value, c3.Value, c4.Value, c5.Value));
         }
-
+        
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -454,14 +456,14 @@ Expression<Func<TSender, T5>> property5
         /// <param name="property4">The 4 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property5">The 5 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Expression<Func<TSender, T3>> property3,
-                        Expression<Func<TSender, T4>> property4,
-                        Expression<Func<TSender, T5>> property5,
-                        Func<T1, T2, T3, T4, T5, TRet> selector)
+        public static IObservable<TRet?> WhenAnyValue<TSender, TRet, T1,T2,T3,T4,T5>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Expression<Func<TSender, T3?>> property3,
+                        Expression<Func<TSender, T4?>> property4,
+                        Expression<Func<TSender, T5?>> property5,
+                        Func<T1?,T2?,T3?,T4?,T5?, TRet> selector)
         {
             return sender.WhenAny(property1, property2, property3, property4, property5,
                                 (c1, c2, c3, c4, c5) =>
@@ -482,24 +484,24 @@ public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5>(
         /// <param name="property4">The 4 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property5">The 5 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5>(
-                this TSender sender,
-                            Expression<Func<TSender, T1>> property1,
-                            Expression<Func<TSender, T2>> property2,
-                            Expression<Func<TSender, T3>> property3,
-                            Expression<Func<TSender, T4>> property4,
-                            Expression<Func<TSender, T5>> property5,
-                            Func<IObservedChange<TSender, T1>, IObservedChange<TSender, T2>, IObservedChange<TSender, T3>, IObservedChange<TSender, T4>, IObservedChange<TSender, T5>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        sender.ObservableForProperty(property1, false, false),
-                        sender.ObservableForProperty(property2, false, false),
-                        sender.ObservableForProperty(property3, false, false),
-                        sender.ObservableForProperty(property4, false, false),
-                        sender.ObservableForProperty(property5, false, false),
-                    selector
-);
-        }
+        public static IObservable<TRet?> WhenAny<TSender, TRet, T1,T2,T3,T4,T5>(
+                this TSender? sender,
+                            Expression<Func<TSender, T1?>> property1,
+                            Expression<Func<TSender, T2?>> property2,
+                            Expression<Func<TSender, T3?>> property3,
+                            Expression<Func<TSender, T4?>> property4,
+                            Expression<Func<TSender, T5?>> property5,
+                            Func<IObservedChange<TSender, T1?>, IObservedChange<TSender, T2?>, IObservedChange<TSender, T3?>, IObservedChange<TSender, T4?>, IObservedChange<TSender, T5?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    sender.ObservableForProperty(property1, false, false),
+                                    sender.ObservableForProperty(property2, false, false),
+                                    sender.ObservableForProperty(property3, false, false),
+                                    sender.ObservableForProperty(property4, false, false),
+                                    sender.ObservableForProperty(property5, false, false),
+                                selector
+            );
+                    }
 
 
         /// <summary>
@@ -516,30 +518,30 @@ public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5>(
         /// <param name="property4">The 4 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property5">The 5 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
-                this TSender sender,
-                            Expression property1,
-                            Expression property2,
-                            Expression property3,
-                            Expression property4,
-                            Expression property5,
-                            Func<IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property1, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property2, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property3, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property4, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property5, false, false),
-                    selector
-);
-        }
-
+        public static IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(
+                this TSender? sender,
+                            Expression? property1,
+                            Expression? property2,
+                            Expression? property3,
+                            Expression? property4,
+                            Expression? property5,
+                            Func<IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property1, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property2, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property3, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property4, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property5, false, false),
+                                selector
+            );
+                    }
+                                                                    
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -554,21 +556,21 @@ public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
         /// <param name="property4">The 4 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property5">The 5 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property6">The 6 property chain to reference. This will be a expression pointing to a end property or field.</param>
-        public static IObservable<(T1, T2, T3, T4, T5, T6)> WhenAnyValue<TSender, T1, T2, T3, T4, T5, T6>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Expression<Func<TSender, T3>> property3,
-                        Expression<Func<TSender, T4>> property4,
-                        Expression<Func<TSender, T5>> property5,
-                        Expression<Func<TSender, T6>> property6
+        public static IObservable<(T1?,T2?,T3?,T4?,T5?,T6?)> WhenAnyValue<TSender, T1,T2,T3,T4,T5,T6>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Expression<Func<TSender, T3?>> property3,
+                        Expression<Func<TSender, T4?>> property4,
+                        Expression<Func<TSender, T5?>> property5,
+                        Expression<Func<TSender, T6?>> property6
             )
         {
             return sender.WhenAny(property1, property2, property3, property4, property5, property6,
                                 (c1, c2, c3, c4, c5, c6) =>
                                     (c1.Value, c2.Value, c3.Value, c4.Value, c5.Value, c6.Value));
         }
-
+        
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -584,15 +586,15 @@ Expression<Func<TSender, T6>> property6
         /// <param name="property5">The 5 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property6">The 6 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Expression<Func<TSender, T3>> property3,
-                        Expression<Func<TSender, T4>> property4,
-                        Expression<Func<TSender, T5>> property5,
-                        Expression<Func<TSender, T6>> property6,
-                        Func<T1, T2, T3, T4, T5, T6, TRet> selector)
+        public static IObservable<TRet?> WhenAnyValue<TSender, TRet, T1,T2,T3,T4,T5,T6>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Expression<Func<TSender, T3?>> property3,
+                        Expression<Func<TSender, T4?>> property4,
+                        Expression<Func<TSender, T5?>> property5,
+                        Expression<Func<TSender, T6?>> property6,
+                        Func<T1?,T2?,T3?,T4?,T5?,T6?, TRet> selector)
         {
             return sender.WhenAny(property1, property2, property3, property4, property5, property6,
                                 (c1, c2, c3, c4, c5, c6) =>
@@ -614,26 +616,26 @@ public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5,
         /// <param name="property5">The 5 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property6">The 6 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6>(
-                this TSender sender,
-                            Expression<Func<TSender, T1>> property1,
-                            Expression<Func<TSender, T2>> property2,
-                            Expression<Func<TSender, T3>> property3,
-                            Expression<Func<TSender, T4>> property4,
-                            Expression<Func<TSender, T5>> property5,
-                            Expression<Func<TSender, T6>> property6,
-                            Func<IObservedChange<TSender, T1>, IObservedChange<TSender, T2>, IObservedChange<TSender, T3>, IObservedChange<TSender, T4>, IObservedChange<TSender, T5>, IObservedChange<TSender, T6>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        sender.ObservableForProperty(property1, false, false),
-                        sender.ObservableForProperty(property2, false, false),
-                        sender.ObservableForProperty(property3, false, false),
-                        sender.ObservableForProperty(property4, false, false),
-                        sender.ObservableForProperty(property5, false, false),
-                        sender.ObservableForProperty(property6, false, false),
-                    selector
-);
-        }
+        public static IObservable<TRet?> WhenAny<TSender, TRet, T1,T2,T3,T4,T5,T6>(
+                this TSender? sender,
+                            Expression<Func<TSender, T1?>> property1,
+                            Expression<Func<TSender, T2?>> property2,
+                            Expression<Func<TSender, T3?>> property3,
+                            Expression<Func<TSender, T4?>> property4,
+                            Expression<Func<TSender, T5?>> property5,
+                            Expression<Func<TSender, T6?>> property6,
+                            Func<IObservedChange<TSender, T1?>, IObservedChange<TSender, T2?>, IObservedChange<TSender, T3?>, IObservedChange<TSender, T4?>, IObservedChange<TSender, T5?>, IObservedChange<TSender, T6?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    sender.ObservableForProperty(property1, false, false),
+                                    sender.ObservableForProperty(property2, false, false),
+                                    sender.ObservableForProperty(property3, false, false),
+                                    sender.ObservableForProperty(property4, false, false),
+                                    sender.ObservableForProperty(property5, false, false),
+                                    sender.ObservableForProperty(property6, false, false),
+                                selector
+            );
+                    }
 
 
         /// <summary>
@@ -651,33 +653,33 @@ public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6>(
         /// <param name="property5">The 5 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property6">The 6 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
-                this TSender sender,
-                            Expression property1,
-                            Expression property2,
-                            Expression property3,
-                            Expression property4,
-                            Expression property5,
-                            Expression property6,
-                            Func<IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property1, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property2, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property3, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property4, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property5, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property6, false, false),
-                    selector
-);
-        }
-
+        public static IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(
+                this TSender? sender,
+                            Expression? property1,
+                            Expression? property2,
+                            Expression? property3,
+                            Expression? property4,
+                            Expression? property5,
+                            Expression? property6,
+                            Func<IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property1, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property2, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property3, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property4, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property5, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property6, false, false),
+                                selector
+            );
+                    }
+                                                                    
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -693,22 +695,22 @@ public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
         /// <param name="property5">The 5 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property6">The 6 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property7">The 7 property chain to reference. This will be a expression pointing to a end property or field.</param>
-        public static IObservable<(T1, T2, T3, T4, T5, T6, T7)> WhenAnyValue<TSender, T1, T2, T3, T4, T5, T6, T7>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Expression<Func<TSender, T3>> property3,
-                        Expression<Func<TSender, T4>> property4,
-                        Expression<Func<TSender, T5>> property5,
-                        Expression<Func<TSender, T6>> property6,
-                        Expression<Func<TSender, T7>> property7
+        public static IObservable<(T1?,T2?,T3?,T4?,T5?,T6?,T7?)> WhenAnyValue<TSender, T1,T2,T3,T4,T5,T6,T7>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Expression<Func<TSender, T3?>> property3,
+                        Expression<Func<TSender, T4?>> property4,
+                        Expression<Func<TSender, T5?>> property5,
+                        Expression<Func<TSender, T6?>> property6,
+                        Expression<Func<TSender, T7?>> property7
             )
         {
             return sender.WhenAny(property1, property2, property3, property4, property5, property6, property7,
                                 (c1, c2, c3, c4, c5, c6, c7) =>
                                     (c1.Value, c2.Value, c3.Value, c4.Value, c5.Value, c6.Value, c7.Value));
         }
-
+        
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -725,16 +727,16 @@ Expression<Func<TSender, T7>> property7
         /// <param name="property6">The 6 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property7">The 7 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Expression<Func<TSender, T3>> property3,
-                        Expression<Func<TSender, T4>> property4,
-                        Expression<Func<TSender, T5>> property5,
-                        Expression<Func<TSender, T6>> property6,
-                        Expression<Func<TSender, T7>> property7,
-                        Func<T1, T2, T3, T4, T5, T6, T7, TRet> selector)
+        public static IObservable<TRet?> WhenAnyValue<TSender, TRet, T1,T2,T3,T4,T5,T6,T7>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Expression<Func<TSender, T3?>> property3,
+                        Expression<Func<TSender, T4?>> property4,
+                        Expression<Func<TSender, T5?>> property5,
+                        Expression<Func<TSender, T6?>> property6,
+                        Expression<Func<TSender, T7?>> property7,
+                        Func<T1?,T2?,T3?,T4?,T5?,T6?,T7?, TRet> selector)
         {
             return sender.WhenAny(property1, property2, property3, property4, property5, property6, property7,
                                 (c1, c2, c3, c4, c5, c6, c7) =>
@@ -757,28 +759,28 @@ public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5,
         /// <param name="property6">The 6 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property7">The 7 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(
-                this TSender sender,
-                            Expression<Func<TSender, T1>> property1,
-                            Expression<Func<TSender, T2>> property2,
-                            Expression<Func<TSender, T3>> property3,
-                            Expression<Func<TSender, T4>> property4,
-                            Expression<Func<TSender, T5>> property5,
-                            Expression<Func<TSender, T6>> property6,
-                            Expression<Func<TSender, T7>> property7,
-                            Func<IObservedChange<TSender, T1>, IObservedChange<TSender, T2>, IObservedChange<TSender, T3>, IObservedChange<TSender, T4>, IObservedChange<TSender, T5>, IObservedChange<TSender, T6>, IObservedChange<TSender, T7>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        sender.ObservableForProperty(property1, false, false),
-                        sender.ObservableForProperty(property2, false, false),
-                        sender.ObservableForProperty(property3, false, false),
-                        sender.ObservableForProperty(property4, false, false),
-                        sender.ObservableForProperty(property5, false, false),
-                        sender.ObservableForProperty(property6, false, false),
-                        sender.ObservableForProperty(property7, false, false),
-                    selector
-);
-        }
+        public static IObservable<TRet?> WhenAny<TSender, TRet, T1,T2,T3,T4,T5,T6,T7>(
+                this TSender? sender,
+                            Expression<Func<TSender, T1?>> property1,
+                            Expression<Func<TSender, T2?>> property2,
+                            Expression<Func<TSender, T3?>> property3,
+                            Expression<Func<TSender, T4?>> property4,
+                            Expression<Func<TSender, T5?>> property5,
+                            Expression<Func<TSender, T6?>> property6,
+                            Expression<Func<TSender, T7?>> property7,
+                            Func<IObservedChange<TSender, T1?>, IObservedChange<TSender, T2?>, IObservedChange<TSender, T3?>, IObservedChange<TSender, T4?>, IObservedChange<TSender, T5?>, IObservedChange<TSender, T6?>, IObservedChange<TSender, T7?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    sender.ObservableForProperty(property1, false, false),
+                                    sender.ObservableForProperty(property2, false, false),
+                                    sender.ObservableForProperty(property3, false, false),
+                                    sender.ObservableForProperty(property4, false, false),
+                                    sender.ObservableForProperty(property5, false, false),
+                                    sender.ObservableForProperty(property6, false, false),
+                                    sender.ObservableForProperty(property7, false, false),
+                                selector
+            );
+                    }
 
 
         /// <summary>
@@ -797,37 +799,37 @@ public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T
         /// <param name="property6">The 6 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property7">The 7 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
-                this TSender sender,
-                            Expression property1,
-                            Expression property2,
-                            Expression property3,
-                            Expression property4,
-                            Expression property5,
-                            Expression property6,
-                            Expression property7,
-                            Func<IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property1, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property2, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property3, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property4, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property5, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property6, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property7, false, false),
-                    selector
-);
-        }
-
-
+        public static IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(
+                this TSender? sender,
+                            Expression? property1,
+                            Expression? property2,
+                            Expression? property3,
+                            Expression? property4,
+                            Expression? property5,
+                            Expression? property6,
+                            Expression? property7,
+                            Func<IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property1, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property2, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property3, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property4, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property5, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property6, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property7, false, false),
+                                selector
+            );
+                    }
+                                                                    
+        
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -845,17 +847,17 @@ public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
         /// <param name="property7">The 7 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property8">The 8 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Expression<Func<TSender, T3>> property3,
-                        Expression<Func<TSender, T4>> property4,
-                        Expression<Func<TSender, T5>> property5,
-                        Expression<Func<TSender, T6>> property6,
-                        Expression<Func<TSender, T7>> property7,
-                        Expression<Func<TSender, T8>> property8,
-                        Func<T1, T2, T3, T4, T5, T6, T7, T8, TRet> selector)
+        public static IObservable<TRet?> WhenAnyValue<TSender, TRet, T1,T2,T3,T4,T5,T6,T7,T8>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Expression<Func<TSender, T3?>> property3,
+                        Expression<Func<TSender, T4?>> property4,
+                        Expression<Func<TSender, T5?>> property5,
+                        Expression<Func<TSender, T6?>> property6,
+                        Expression<Func<TSender, T7?>> property7,
+                        Expression<Func<TSender, T8?>> property8,
+                        Func<T1?,T2?,T3?,T4?,T5?,T6?,T7?,T8?, TRet> selector)
         {
             return sender.WhenAny(property1, property2, property3, property4, property5, property6, property7, property8,
                                 (c1, c2, c3, c4, c5, c6, c7, c8) =>
@@ -879,30 +881,30 @@ public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5,
         /// <param name="property7">The 7 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property8">The 8 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(
-                this TSender sender,
-                            Expression<Func<TSender, T1>> property1,
-                            Expression<Func<TSender, T2>> property2,
-                            Expression<Func<TSender, T3>> property3,
-                            Expression<Func<TSender, T4>> property4,
-                            Expression<Func<TSender, T5>> property5,
-                            Expression<Func<TSender, T6>> property6,
-                            Expression<Func<TSender, T7>> property7,
-                            Expression<Func<TSender, T8>> property8,
-                            Func<IObservedChange<TSender, T1>, IObservedChange<TSender, T2>, IObservedChange<TSender, T3>, IObservedChange<TSender, T4>, IObservedChange<TSender, T5>, IObservedChange<TSender, T6>, IObservedChange<TSender, T7>, IObservedChange<TSender, T8>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        sender.ObservableForProperty(property1, false, false),
-                        sender.ObservableForProperty(property2, false, false),
-                        sender.ObservableForProperty(property3, false, false),
-                        sender.ObservableForProperty(property4, false, false),
-                        sender.ObservableForProperty(property5, false, false),
-                        sender.ObservableForProperty(property6, false, false),
-                        sender.ObservableForProperty(property7, false, false),
-                        sender.ObservableForProperty(property8, false, false),
-                    selector
-);
-        }
+        public static IObservable<TRet?> WhenAny<TSender, TRet, T1,T2,T3,T4,T5,T6,T7,T8>(
+                this TSender? sender,
+                            Expression<Func<TSender, T1?>> property1,
+                            Expression<Func<TSender, T2?>> property2,
+                            Expression<Func<TSender, T3?>> property3,
+                            Expression<Func<TSender, T4?>> property4,
+                            Expression<Func<TSender, T5?>> property5,
+                            Expression<Func<TSender, T6?>> property6,
+                            Expression<Func<TSender, T7?>> property7,
+                            Expression<Func<TSender, T8?>> property8,
+                            Func<IObservedChange<TSender, T1?>, IObservedChange<TSender, T2?>, IObservedChange<TSender, T3?>, IObservedChange<TSender, T4?>, IObservedChange<TSender, T5?>, IObservedChange<TSender, T6?>, IObservedChange<TSender, T7?>, IObservedChange<TSender, T8?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    sender.ObservableForProperty(property1, false, false),
+                                    sender.ObservableForProperty(property2, false, false),
+                                    sender.ObservableForProperty(property3, false, false),
+                                    sender.ObservableForProperty(property4, false, false),
+                                    sender.ObservableForProperty(property5, false, false),
+                                    sender.ObservableForProperty(property6, false, false),
+                                    sender.ObservableForProperty(property7, false, false),
+                                    sender.ObservableForProperty(property8, false, false),
+                                selector
+            );
+                    }
 
 
         /// <summary>
@@ -922,40 +924,40 @@ public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T
         /// <param name="property7">The 7 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property8">The 8 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
-                this TSender sender,
-                            Expression property1,
-                            Expression property2,
-                            Expression property3,
-                            Expression property4,
-                            Expression property5,
-                            Expression property6,
-                            Expression property7,
-                            Expression property8,
-                            Func<IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property1, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property2, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property3, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property4, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property5, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property6, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property7, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property8, false, false),
-                    selector
-);
-        }
-
-
+        public static IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(
+                this TSender? sender,
+                            Expression? property1,
+                            Expression? property2,
+                            Expression? property3,
+                            Expression? property4,
+                            Expression? property5,
+                            Expression? property6,
+                            Expression? property7,
+                            Expression? property8,
+                            Func<IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property1, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property2, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property3, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property4, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property5, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property6, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property7, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property8, false, false),
+                                selector
+            );
+                    }
+                                                                    
+        
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -974,18 +976,18 @@ public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
         /// <param name="property8">The 8 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property9">The 9 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Expression<Func<TSender, T3>> property3,
-                        Expression<Func<TSender, T4>> property4,
-                        Expression<Func<TSender, T5>> property5,
-                        Expression<Func<TSender, T6>> property6,
-                        Expression<Func<TSender, T7>> property7,
-                        Expression<Func<TSender, T8>> property8,
-                        Expression<Func<TSender, T9>> property9,
-                        Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, TRet> selector)
+        public static IObservable<TRet?> WhenAnyValue<TSender, TRet, T1,T2,T3,T4,T5,T6,T7,T8,T9>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Expression<Func<TSender, T3?>> property3,
+                        Expression<Func<TSender, T4?>> property4,
+                        Expression<Func<TSender, T5?>> property5,
+                        Expression<Func<TSender, T6?>> property6,
+                        Expression<Func<TSender, T7?>> property7,
+                        Expression<Func<TSender, T8?>> property8,
+                        Expression<Func<TSender, T9?>> property9,
+                        Func<T1?,T2?,T3?,T4?,T5?,T6?,T7?,T8?,T9?, TRet> selector)
         {
             return sender.WhenAny(property1, property2, property3, property4, property5, property6, property7, property8, property9,
                                 (c1, c2, c3, c4, c5, c6, c7, c8, c9) =>
@@ -1010,32 +1012,32 @@ public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5,
         /// <param name="property8">The 8 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property9">The 9 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(
-                this TSender sender,
-                            Expression<Func<TSender, T1>> property1,
-                            Expression<Func<TSender, T2>> property2,
-                            Expression<Func<TSender, T3>> property3,
-                            Expression<Func<TSender, T4>> property4,
-                            Expression<Func<TSender, T5>> property5,
-                            Expression<Func<TSender, T6>> property6,
-                            Expression<Func<TSender, T7>> property7,
-                            Expression<Func<TSender, T8>> property8,
-                            Expression<Func<TSender, T9>> property9,
-                            Func<IObservedChange<TSender, T1>, IObservedChange<TSender, T2>, IObservedChange<TSender, T3>, IObservedChange<TSender, T4>, IObservedChange<TSender, T5>, IObservedChange<TSender, T6>, IObservedChange<TSender, T7>, IObservedChange<TSender, T8>, IObservedChange<TSender, T9>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        sender.ObservableForProperty(property1, false, false),
-                        sender.ObservableForProperty(property2, false, false),
-                        sender.ObservableForProperty(property3, false, false),
-                        sender.ObservableForProperty(property4, false, false),
-                        sender.ObservableForProperty(property5, false, false),
-                        sender.ObservableForProperty(property6, false, false),
-                        sender.ObservableForProperty(property7, false, false),
-                        sender.ObservableForProperty(property8, false, false),
-                        sender.ObservableForProperty(property9, false, false),
-                    selector
-);
-        }
+        public static IObservable<TRet?> WhenAny<TSender, TRet, T1,T2,T3,T4,T5,T6,T7,T8,T9>(
+                this TSender? sender,
+                            Expression<Func<TSender, T1?>> property1,
+                            Expression<Func<TSender, T2?>> property2,
+                            Expression<Func<TSender, T3?>> property3,
+                            Expression<Func<TSender, T4?>> property4,
+                            Expression<Func<TSender, T5?>> property5,
+                            Expression<Func<TSender, T6?>> property6,
+                            Expression<Func<TSender, T7?>> property7,
+                            Expression<Func<TSender, T8?>> property8,
+                            Expression<Func<TSender, T9?>> property9,
+                            Func<IObservedChange<TSender, T1?>, IObservedChange<TSender, T2?>, IObservedChange<TSender, T3?>, IObservedChange<TSender, T4?>, IObservedChange<TSender, T5?>, IObservedChange<TSender, T6?>, IObservedChange<TSender, T7?>, IObservedChange<TSender, T8?>, IObservedChange<TSender, T9?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    sender.ObservableForProperty(property1, false, false),
+                                    sender.ObservableForProperty(property2, false, false),
+                                    sender.ObservableForProperty(property3, false, false),
+                                    sender.ObservableForProperty(property4, false, false),
+                                    sender.ObservableForProperty(property5, false, false),
+                                    sender.ObservableForProperty(property6, false, false),
+                                    sender.ObservableForProperty(property7, false, false),
+                                    sender.ObservableForProperty(property8, false, false),
+                                    sender.ObservableForProperty(property9, false, false),
+                                selector
+            );
+                    }
 
 
         /// <summary>
@@ -1056,43 +1058,43 @@ public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T
         /// <param name="property8">The 8 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property9">The 9 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
-                this TSender sender,
-                            Expression property1,
-                            Expression property2,
-                            Expression property3,
-                            Expression property4,
-                            Expression property5,
-                            Expression property6,
-                            Expression property7,
-                            Expression property8,
-                            Expression property9,
-                            Func<IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property1, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property2, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property3, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property4, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property5, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property6, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property7, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property8, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property9, false, false),
-                    selector
-);
-        }
-
-
+        public static IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(
+                this TSender? sender,
+                            Expression? property1,
+                            Expression? property2,
+                            Expression? property3,
+                            Expression? property4,
+                            Expression? property5,
+                            Expression? property6,
+                            Expression? property7,
+                            Expression? property8,
+                            Expression? property9,
+                            Func<IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property1, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property2, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property3, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property4, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property5, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property6, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property7, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property8, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property9, false, false),
+                                selector
+            );
+                    }
+                                                                    
+        
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -1112,19 +1114,19 @@ public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
         /// <param name="property9">The 9 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property10">The 10 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Expression<Func<TSender, T3>> property3,
-                        Expression<Func<TSender, T4>> property4,
-                        Expression<Func<TSender, T5>> property5,
-                        Expression<Func<TSender, T6>> property6,
-                        Expression<Func<TSender, T7>> property7,
-                        Expression<Func<TSender, T8>> property8,
-                        Expression<Func<TSender, T9>> property9,
-                        Expression<Func<TSender, T10>> property10,
-                        Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TRet> selector)
+        public static IObservable<TRet?> WhenAnyValue<TSender, TRet, T1,T2,T3,T4,T5,T6,T7,T8,T9,T10>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Expression<Func<TSender, T3?>> property3,
+                        Expression<Func<TSender, T4?>> property4,
+                        Expression<Func<TSender, T5?>> property5,
+                        Expression<Func<TSender, T6?>> property6,
+                        Expression<Func<TSender, T7?>> property7,
+                        Expression<Func<TSender, T8?>> property8,
+                        Expression<Func<TSender, T9?>> property9,
+                        Expression<Func<TSender, T10?>> property10,
+                        Func<T1?,T2?,T3?,T4?,T5?,T6?,T7?,T8?,T9?,T10?, TRet> selector)
         {
             return sender.WhenAny(property1, property2, property3, property4, property5, property6, property7, property8, property9, property10,
                                 (c1, c2, c3, c4, c5, c6, c7, c8, c9, c10) =>
@@ -1150,34 +1152,34 @@ public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5,
         /// <param name="property9">The 9 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property10">The 10 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(
-                this TSender sender,
-                            Expression<Func<TSender, T1>> property1,
-                            Expression<Func<TSender, T2>> property2,
-                            Expression<Func<TSender, T3>> property3,
-                            Expression<Func<TSender, T4>> property4,
-                            Expression<Func<TSender, T5>> property5,
-                            Expression<Func<TSender, T6>> property6,
-                            Expression<Func<TSender, T7>> property7,
-                            Expression<Func<TSender, T8>> property8,
-                            Expression<Func<TSender, T9>> property9,
-                            Expression<Func<TSender, T10>> property10,
-                            Func<IObservedChange<TSender, T1>, IObservedChange<TSender, T2>, IObservedChange<TSender, T3>, IObservedChange<TSender, T4>, IObservedChange<TSender, T5>, IObservedChange<TSender, T6>, IObservedChange<TSender, T7>, IObservedChange<TSender, T8>, IObservedChange<TSender, T9>, IObservedChange<TSender, T10>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        sender.ObservableForProperty(property1, false, false),
-                        sender.ObservableForProperty(property2, false, false),
-                        sender.ObservableForProperty(property3, false, false),
-                        sender.ObservableForProperty(property4, false, false),
-                        sender.ObservableForProperty(property5, false, false),
-                        sender.ObservableForProperty(property6, false, false),
-                        sender.ObservableForProperty(property7, false, false),
-                        sender.ObservableForProperty(property8, false, false),
-                        sender.ObservableForProperty(property9, false, false),
-                        sender.ObservableForProperty(property10, false, false),
-                    selector
-);
-        }
+        public static IObservable<TRet?> WhenAny<TSender, TRet, T1,T2,T3,T4,T5,T6,T7,T8,T9,T10>(
+                this TSender? sender,
+                            Expression<Func<TSender, T1?>> property1,
+                            Expression<Func<TSender, T2?>> property2,
+                            Expression<Func<TSender, T3?>> property3,
+                            Expression<Func<TSender, T4?>> property4,
+                            Expression<Func<TSender, T5?>> property5,
+                            Expression<Func<TSender, T6?>> property6,
+                            Expression<Func<TSender, T7?>> property7,
+                            Expression<Func<TSender, T8?>> property8,
+                            Expression<Func<TSender, T9?>> property9,
+                            Expression<Func<TSender, T10?>> property10,
+                            Func<IObservedChange<TSender, T1?>, IObservedChange<TSender, T2?>, IObservedChange<TSender, T3?>, IObservedChange<TSender, T4?>, IObservedChange<TSender, T5?>, IObservedChange<TSender, T6?>, IObservedChange<TSender, T7?>, IObservedChange<TSender, T8?>, IObservedChange<TSender, T9?>, IObservedChange<TSender, T10?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    sender.ObservableForProperty(property1, false, false),
+                                    sender.ObservableForProperty(property2, false, false),
+                                    sender.ObservableForProperty(property3, false, false),
+                                    sender.ObservableForProperty(property4, false, false),
+                                    sender.ObservableForProperty(property5, false, false),
+                                    sender.ObservableForProperty(property6, false, false),
+                                    sender.ObservableForProperty(property7, false, false),
+                                    sender.ObservableForProperty(property8, false, false),
+                                    sender.ObservableForProperty(property9, false, false),
+                                    sender.ObservableForProperty(property10, false, false),
+                                selector
+            );
+                    }
 
 
         /// <summary>
@@ -1199,46 +1201,46 @@ public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T
         /// <param name="property9">The 9 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property10">The 10 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
-                this TSender sender,
-                            Expression property1,
-                            Expression property2,
-                            Expression property3,
-                            Expression property4,
-                            Expression property5,
-                            Expression property6,
-                            Expression property7,
-                            Expression property8,
-                            Expression property9,
-                            Expression property10,
-                            Func<IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property1, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property2, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property3, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property4, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property5, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property6, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property7, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property8, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property9, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property10, false, false),
-                    selector
-);
-        }
-
-
+        public static IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(
+                this TSender? sender,
+                            Expression? property1,
+                            Expression? property2,
+                            Expression? property3,
+                            Expression? property4,
+                            Expression? property5,
+                            Expression? property6,
+                            Expression? property7,
+                            Expression? property8,
+                            Expression? property9,
+                            Expression? property10,
+                            Func<IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property1, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property2, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property3, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property4, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property5, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property6, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property7, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property8, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property9, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property10, false, false),
+                                selector
+            );
+                    }
+                                                                    
+        
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -1259,20 +1261,20 @@ public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
         /// <param name="property10">The 10 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property11">The 11 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Expression<Func<TSender, T3>> property3,
-                        Expression<Func<TSender, T4>> property4,
-                        Expression<Func<TSender, T5>> property5,
-                        Expression<Func<TSender, T6>> property6,
-                        Expression<Func<TSender, T7>> property7,
-                        Expression<Func<TSender, T8>> property8,
-                        Expression<Func<TSender, T9>> property9,
-                        Expression<Func<TSender, T10>> property10,
-                        Expression<Func<TSender, T11>> property11,
-                        Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, TRet> selector)
+        public static IObservable<TRet?> WhenAnyValue<TSender, TRet, T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Expression<Func<TSender, T3?>> property3,
+                        Expression<Func<TSender, T4?>> property4,
+                        Expression<Func<TSender, T5?>> property5,
+                        Expression<Func<TSender, T6?>> property6,
+                        Expression<Func<TSender, T7?>> property7,
+                        Expression<Func<TSender, T8?>> property8,
+                        Expression<Func<TSender, T9?>> property9,
+                        Expression<Func<TSender, T10?>> property10,
+                        Expression<Func<TSender, T11?>> property11,
+                        Func<T1?,T2?,T3?,T4?,T5?,T6?,T7?,T8?,T9?,T10?,T11?, TRet> selector)
         {
             return sender.WhenAny(property1, property2, property3, property4, property5, property6, property7, property8, property9, property10, property11,
                                 (c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11) =>
@@ -1299,36 +1301,36 @@ public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5,
         /// <param name="property10">The 10 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property11">The 11 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(
-                this TSender sender,
-                            Expression<Func<TSender, T1>> property1,
-                            Expression<Func<TSender, T2>> property2,
-                            Expression<Func<TSender, T3>> property3,
-                            Expression<Func<TSender, T4>> property4,
-                            Expression<Func<TSender, T5>> property5,
-                            Expression<Func<TSender, T6>> property6,
-                            Expression<Func<TSender, T7>> property7,
-                            Expression<Func<TSender, T8>> property8,
-                            Expression<Func<TSender, T9>> property9,
-                            Expression<Func<TSender, T10>> property10,
-                            Expression<Func<TSender, T11>> property11,
-                            Func<IObservedChange<TSender, T1>, IObservedChange<TSender, T2>, IObservedChange<TSender, T3>, IObservedChange<TSender, T4>, IObservedChange<TSender, T5>, IObservedChange<TSender, T6>, IObservedChange<TSender, T7>, IObservedChange<TSender, T8>, IObservedChange<TSender, T9>, IObservedChange<TSender, T10>, IObservedChange<TSender, T11>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        sender.ObservableForProperty(property1, false, false),
-                        sender.ObservableForProperty(property2, false, false),
-                        sender.ObservableForProperty(property3, false, false),
-                        sender.ObservableForProperty(property4, false, false),
-                        sender.ObservableForProperty(property5, false, false),
-                        sender.ObservableForProperty(property6, false, false),
-                        sender.ObservableForProperty(property7, false, false),
-                        sender.ObservableForProperty(property8, false, false),
-                        sender.ObservableForProperty(property9, false, false),
-                        sender.ObservableForProperty(property10, false, false),
-                        sender.ObservableForProperty(property11, false, false),
-                    selector
-);
-        }
+        public static IObservable<TRet?> WhenAny<TSender, TRet, T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11>(
+                this TSender? sender,
+                            Expression<Func<TSender, T1?>> property1,
+                            Expression<Func<TSender, T2?>> property2,
+                            Expression<Func<TSender, T3?>> property3,
+                            Expression<Func<TSender, T4?>> property4,
+                            Expression<Func<TSender, T5?>> property5,
+                            Expression<Func<TSender, T6?>> property6,
+                            Expression<Func<TSender, T7?>> property7,
+                            Expression<Func<TSender, T8?>> property8,
+                            Expression<Func<TSender, T9?>> property9,
+                            Expression<Func<TSender, T10?>> property10,
+                            Expression<Func<TSender, T11?>> property11,
+                            Func<IObservedChange<TSender, T1?>, IObservedChange<TSender, T2?>, IObservedChange<TSender, T3?>, IObservedChange<TSender, T4?>, IObservedChange<TSender, T5?>, IObservedChange<TSender, T6?>, IObservedChange<TSender, T7?>, IObservedChange<TSender, T8?>, IObservedChange<TSender, T9?>, IObservedChange<TSender, T10?>, IObservedChange<TSender, T11?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    sender.ObservableForProperty(property1, false, false),
+                                    sender.ObservableForProperty(property2, false, false),
+                                    sender.ObservableForProperty(property3, false, false),
+                                    sender.ObservableForProperty(property4, false, false),
+                                    sender.ObservableForProperty(property5, false, false),
+                                    sender.ObservableForProperty(property6, false, false),
+                                    sender.ObservableForProperty(property7, false, false),
+                                    sender.ObservableForProperty(property8, false, false),
+                                    sender.ObservableForProperty(property9, false, false),
+                                    sender.ObservableForProperty(property10, false, false),
+                                    sender.ObservableForProperty(property11, false, false),
+                                selector
+            );
+                    }
 
 
         /// <summary>
@@ -1351,49 +1353,49 @@ public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T
         /// <param name="property10">The 10 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property11">The 11 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
-                this TSender sender,
-                            Expression property1,
-                            Expression property2,
-                            Expression property3,
-                            Expression property4,
-                            Expression property5,
-                            Expression property6,
-                            Expression property7,
-                            Expression property8,
-                            Expression property9,
-                            Expression property10,
-                            Expression property11,
-                            Func<IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property1, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property2, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property3, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property4, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property5, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property6, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property7, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property8, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property9, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property10, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property11, false, false),
-                    selector
-);
-        }
-
-
+        public static IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(
+                this TSender? sender,
+                            Expression? property1,
+                            Expression? property2,
+                            Expression? property3,
+                            Expression? property4,
+                            Expression? property5,
+                            Expression? property6,
+                            Expression? property7,
+                            Expression? property8,
+                            Expression? property9,
+                            Expression? property10,
+                            Expression? property11,
+                            Func<IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property1, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property2, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property3, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property4, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property5, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property6, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property7, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property8, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property9, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property10, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property11, false, false),
+                                selector
+            );
+                    }
+                                                                    
+        
         /// <summary>
         /// WhenAnyValue allows you to observe whenever the value of one or more
         /// properties on an object have changed, providing an initial value when
@@ -1415,21 +1417,21 @@ public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
         /// <param name="property11">The 11 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property12">The 12 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(
-            this TSender sender,
-                        Expression<Func<TSender, T1>> property1,
-                        Expression<Func<TSender, T2>> property2,
-                        Expression<Func<TSender, T3>> property3,
-                        Expression<Func<TSender, T4>> property4,
-                        Expression<Func<TSender, T5>> property5,
-                        Expression<Func<TSender, T6>> property6,
-                        Expression<Func<TSender, T7>> property7,
-                        Expression<Func<TSender, T8>> property8,
-                        Expression<Func<TSender, T9>> property9,
-                        Expression<Func<TSender, T10>> property10,
-                        Expression<Func<TSender, T11>> property11,
-                        Expression<Func<TSender, T12>> property12,
-                        Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, TRet> selector)
+        public static IObservable<TRet?> WhenAnyValue<TSender, TRet, T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12>(
+            this TSender? sender,
+                        Expression<Func<TSender, T1?>> property1,
+                        Expression<Func<TSender, T2?>> property2,
+                        Expression<Func<TSender, T3?>> property3,
+                        Expression<Func<TSender, T4?>> property4,
+                        Expression<Func<TSender, T5?>> property5,
+                        Expression<Func<TSender, T6?>> property6,
+                        Expression<Func<TSender, T7?>> property7,
+                        Expression<Func<TSender, T8?>> property8,
+                        Expression<Func<TSender, T9?>> property9,
+                        Expression<Func<TSender, T10?>> property10,
+                        Expression<Func<TSender, T11?>> property11,
+                        Expression<Func<TSender, T12?>> property12,
+                        Func<T1?,T2?,T3?,T4?,T5?,T6?,T7?,T8?,T9?,T10?,T11?,T12?, TRet> selector)
         {
             return sender.WhenAny(property1, property2, property3, property4, property5, property6, property7, property8, property9, property10, property11, property12,
                                 (c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11, c12) =>
@@ -1457,38 +1459,38 @@ public static IObservable<TRet> WhenAnyValue<TSender, TRet, T1, T2, T3, T4, T5,
         /// <param name="property11">The 11 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property12">The 12 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(
-                this TSender sender,
-                            Expression<Func<TSender, T1>> property1,
-                            Expression<Func<TSender, T2>> property2,
-                            Expression<Func<TSender, T3>> property3,
-                            Expression<Func<TSender, T4>> property4,
-                            Expression<Func<TSender, T5>> property5,
-                            Expression<Func<TSender, T6>> property6,
-                            Expression<Func<TSender, T7>> property7,
-                            Expression<Func<TSender, T8>> property8,
-                            Expression<Func<TSender, T9>> property9,
-                            Expression<Func<TSender, T10>> property10,
-                            Expression<Func<TSender, T11>> property11,
-                            Expression<Func<TSender, T12>> property12,
-                            Func<IObservedChange<TSender, T1>, IObservedChange<TSender, T2>, IObservedChange<TSender, T3>, IObservedChange<TSender, T4>, IObservedChange<TSender, T5>, IObservedChange<TSender, T6>, IObservedChange<TSender, T7>, IObservedChange<TSender, T8>, IObservedChange<TSender, T9>, IObservedChange<TSender, T10>, IObservedChange<TSender, T11>, IObservedChange<TSender, T12>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        sender.ObservableForProperty(property1, false, false),
-                        sender.ObservableForProperty(property2, false, false),
-                        sender.ObservableForProperty(property3, false, false),
-                        sender.ObservableForProperty(property4, false, false),
-                        sender.ObservableForProperty(property5, false, false),
-                        sender.ObservableForProperty(property6, false, false),
-                        sender.ObservableForProperty(property7, false, false),
-                        sender.ObservableForProperty(property8, false, false),
-                        sender.ObservableForProperty(property9, false, false),
-                        sender.ObservableForProperty(property10, false, false),
-                        sender.ObservableForProperty(property11, false, false),
-                        sender.ObservableForProperty(property12, false, false),
-                    selector
-);
-        }
+        public static IObservable<TRet?> WhenAny<TSender, TRet, T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12>(
+                this TSender? sender,
+                            Expression<Func<TSender, T1?>> property1,
+                            Expression<Func<TSender, T2?>> property2,
+                            Expression<Func<TSender, T3?>> property3,
+                            Expression<Func<TSender, T4?>> property4,
+                            Expression<Func<TSender, T5?>> property5,
+                            Expression<Func<TSender, T6?>> property6,
+                            Expression<Func<TSender, T7?>> property7,
+                            Expression<Func<TSender, T8?>> property8,
+                            Expression<Func<TSender, T9?>> property9,
+                            Expression<Func<TSender, T10?>> property10,
+                            Expression<Func<TSender, T11?>> property11,
+                            Expression<Func<TSender, T12?>> property12,
+                            Func<IObservedChange<TSender, T1?>, IObservedChange<TSender, T2?>, IObservedChange<TSender, T3?>, IObservedChange<TSender, T4?>, IObservedChange<TSender, T5?>, IObservedChange<TSender, T6?>, IObservedChange<TSender, T7?>, IObservedChange<TSender, T8?>, IObservedChange<TSender, T9?>, IObservedChange<TSender, T10?>, IObservedChange<TSender, T11?>, IObservedChange<TSender, T12?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    sender.ObservableForProperty(property1, false, false),
+                                    sender.ObservableForProperty(property2, false, false),
+                                    sender.ObservableForProperty(property3, false, false),
+                                    sender.ObservableForProperty(property4, false, false),
+                                    sender.ObservableForProperty(property5, false, false),
+                                    sender.ObservableForProperty(property6, false, false),
+                                    sender.ObservableForProperty(property7, false, false),
+                                    sender.ObservableForProperty(property8, false, false),
+                                    sender.ObservableForProperty(property9, false, false),
+                                    sender.ObservableForProperty(property10, false, false),
+                                    sender.ObservableForProperty(property11, false, false),
+                                    sender.ObservableForProperty(property12, false, false),
+                                selector
+            );
+                    }
 
 
         /// <summary>
@@ -1512,51 +1514,51 @@ public static IObservable<TRet> WhenAny<TSender, TRet, T1, T2, T3, T4, T5, T6, T
         /// <param name="property11">The 11 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="property12">The 12 property chain to reference. This will be a expression pointing to a end property or field.</param>
         /// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
-                this TSender sender,
-                            Expression property1,
-                            Expression property2,
-                            Expression property3,
-                            Expression property4,
-                            Expression property5,
-                            Expression property6,
-                            Expression property7,
-                            Expression property8,
-                            Expression property9,
-                            Expression property10,
-                            Expression property11,
-                            Expression property12,
-                            Func<IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, IObservedChange<TSender, object>, TRet> selector)
-        {
-            return Observable.CombineLatest(
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property1, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property2, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property3, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property4, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property5, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property6, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property7, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property8, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property9, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property10, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property11, false, false),
-                        ReactiveNotifyPropertyChangedMixin
-            .SubscribeToExpressionChain<TSender, object>(sender, property12, false, false),
-                    selector
-);
+        public static IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(
+                this TSender? sender,
+                            Expression? property1,
+                            Expression? property2,
+                            Expression? property3,
+                            Expression? property4,
+                            Expression? property5,
+                            Expression? property6,
+                            Expression? property7,
+                            Expression? property8,
+                            Expression? property9,
+                            Expression? property10,
+                            Expression? property11,
+                            Expression? property12,
+                            Func<IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, IObservedChange<TSender?, object?>, TRet?> selector)
+        {
+                        return Observable.CombineLatest(
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property1, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property2, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property3, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property4, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property5, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property6, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property7, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property8, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property9, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property10, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property11, false, false),
+                                    ReactiveNotifyPropertyChangedMixin
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property12, false, false),
+                                selector
+            );
+                    }
         }
-    }
 
     /// <summary>A mixin which provides support for subscribing to observable properties.</summary>
     public static class WhenAnyObservableMixin
@@ -1564,32 +1566,32 @@ public static class WhenAnyObservableMixin
         /// <summary>Observe a observable which is set to a property, and automatically subscribe to the most recent emitted value.</summary>
         /// <param name="sender">The object where the property chain starts.</param>
         /// <param name="obs1">The first observable to observe.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, Expression<Func<TSender, IObservable<TRet>>> obs1)
+        public static IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, Expression<Func<TSender, IObservable<TRet>?>> obs1)
             where TSender : class
         {
-            return sender.WhenAny(obs1, x => x.Value.EmptyIfNull()).Switch();
+            return sender!.WhenAny(obs1, x => x.Value!.EmptyIfNull())!.Switch();
         }
 
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
         /// <param name="sender">The object where the property chain starts.</param>
         /// <param name="obs1">The 1 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs2">The 2 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, Expression<Func<TSender, IObservable<TRet>>> obs1, Expression<Func<TSender, IObservable<TRet>>> obs2)
-    where TSender : class
+                public static IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, Expression<Func<TSender, IObservable<TRet>?>> obs1, Expression<Func<TSender, IObservable<TRet>?>> obs2)
+            where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, (o1, o2) => new[] { o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull() })
-                .Select(x => x.Merge()).Switch();
+            return sender!.WhenAny(obs1, obs2, (o1, o2) => new[] {o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull()})
+                .Select(x => x?.Merge())!.Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
         /// <param name="sender">The object where the property chain starts.</param>
         /// <param name="obs1">The 1 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs2">The 2 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs3">The 3 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, Expression<Func<TSender, IObservable<TRet>>> obs1, Expression<Func<TSender, IObservable<TRet>>> obs2, Expression<Func<TSender, IObservable<TRet>>> obs3)
-    where TSender : class
+                public static IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, Expression<Func<TSender, IObservable<TRet>?>> obs1, Expression<Func<TSender, IObservable<TRet>?>> obs2, Expression<Func<TSender, IObservable<TRet>?>> obs3)
+            where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, (o1, o2, o3) => new[] { o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull() })
-                .Select(x => x.Merge()).Switch();
+            return sender!.WhenAny(obs1, obs2, obs3, (o1, o2, o3) => new[] {o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull()})
+                .Select(x => x?.Merge())!.Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
         /// <param name="sender">The object where the property chain starts.</param>
@@ -1597,11 +1599,11 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender se
         /// <param name="obs2">The 2 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs3">The 3 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs4">The 4 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, Expression<Func<TSender, IObservable<TRet>>> obs1, Expression<Func<TSender, IObservable<TRet>>> obs2, Expression<Func<TSender, IObservable<TRet>>> obs3, Expression<Func<TSender, IObservable<TRet>>> obs4)
-    where TSender : class
+                public static IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, Expression<Func<TSender, IObservable<TRet>?>> obs1, Expression<Func<TSender, IObservable<TRet>?>> obs2, Expression<Func<TSender, IObservable<TRet>?>> obs3, Expression<Func<TSender, IObservable<TRet>?>> obs4)
+            where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, (o1, o2, o3, o4) => new[] { o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull() })
-                .Select(x => x.Merge()).Switch();
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, (o1, o2, o3, o4) => new[] {o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull()})
+                .Select(x => x?.Merge())!.Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
         /// <param name="sender">The object where the property chain starts.</param>
@@ -1610,11 +1612,11 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender se
         /// <param name="obs3">The 3 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs4">The 4 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs5">The 5 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, Expression<Func<TSender, IObservable<TRet>>> obs1, Expression<Func<TSender, IObservable<TRet>>> obs2, Expression<Func<TSender, IObservable<TRet>>> obs3, Expression<Func<TSender, IObservable<TRet>>> obs4, Expression<Func<TSender, IObservable<TRet>>> obs5)
-    where TSender : class
+                public static IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, Expression<Func<TSender, IObservable<TRet>?>> obs1, Expression<Func<TSender, IObservable<TRet>?>> obs2, Expression<Func<TSender, IObservable<TRet>?>> obs3, Expression<Func<TSender, IObservable<TRet>?>> obs4, Expression<Func<TSender, IObservable<TRet>?>> obs5)
+            where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, (o1, o2, o3, o4, o5) => new[] { o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull() })
-                .Select(x => x.Merge()).Switch();
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, (o1, o2, o3, o4, o5) => new[] {o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull()})
+                .Select(x => x?.Merge())!.Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
         /// <param name="sender">The object where the property chain starts.</param>
@@ -1624,11 +1626,11 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender se
         /// <param name="obs4">The 4 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs5">The 5 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs6">The 6 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, Expression<Func<TSender, IObservable<TRet>>> obs1, Expression<Func<TSender, IObservable<TRet>>> obs2, Expression<Func<TSender, IObservable<TRet>>> obs3, Expression<Func<TSender, IObservable<TRet>>> obs4, Expression<Func<TSender, IObservable<TRet>>> obs5, Expression<Func<TSender, IObservable<TRet>>> obs6)
-    where TSender : class
+                public static IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, Expression<Func<TSender, IObservable<TRet>?>> obs1, Expression<Func<TSender, IObservable<TRet>?>> obs2, Expression<Func<TSender, IObservable<TRet>?>> obs3, Expression<Func<TSender, IObservable<TRet>?>> obs4, Expression<Func<TSender, IObservable<TRet>?>> obs5, Expression<Func<TSender, IObservable<TRet>?>> obs6)
+            where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, (o1, o2, o3, o4, o5, o6) => new[] { o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull(), o6.Value.EmptyIfNull() })
-                .Select(x => x.Merge()).Switch();
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, (o1, o2, o3, o4, o5, o6) => new[] {o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull(), o6.Value!.EmptyIfNull()})
+                .Select(x => x?.Merge())!.Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
         /// <param name="sender">The object where the property chain starts.</param>
@@ -1639,11 +1641,11 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender se
         /// <param name="obs5">The 5 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs6">The 6 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs7">The 7 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, Expression<Func<TSender, IObservable<TRet>>> obs1, Expression<Func<TSender, IObservable<TRet>>> obs2, Expression<Func<TSender, IObservable<TRet>>> obs3, Expression<Func<TSender, IObservable<TRet>>> obs4, Expression<Func<TSender, IObservable<TRet>>> obs5, Expression<Func<TSender, IObservable<TRet>>> obs6, Expression<Func<TSender, IObservable<TRet>>> obs7)
-    where TSender : class
+                public static IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, Expression<Func<TSender, IObservable<TRet>?>> obs1, Expression<Func<TSender, IObservable<TRet>?>> obs2, Expression<Func<TSender, IObservable<TRet>?>> obs3, Expression<Func<TSender, IObservable<TRet>?>> obs4, Expression<Func<TSender, IObservable<TRet>?>> obs5, Expression<Func<TSender, IObservable<TRet>?>> obs6, Expression<Func<TSender, IObservable<TRet>?>> obs7)
+            where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, (o1, o2, o3, o4, o5, o6, o7) => new[] { o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull(), o6.Value.EmptyIfNull(), o7.Value.EmptyIfNull() })
-                .Select(x => x.Merge()).Switch();
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, (o1, o2, o3, o4, o5, o6, o7) => new[] {o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull(), o6.Value!.EmptyIfNull(), o7.Value!.EmptyIfNull()})
+                .Select(x => x?.Merge())!.Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
         /// <param name="sender">The object where the property chain starts.</param>
@@ -1655,11 +1657,11 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender se
         /// <param name="obs6">The 6 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs7">The 7 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs8">The 8 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, Expression<Func<TSender, IObservable<TRet>>> obs1, Expression<Func<TSender, IObservable<TRet>>> obs2, Expression<Func<TSender, IObservable<TRet>>> obs3, Expression<Func<TSender, IObservable<TRet>>> obs4, Expression<Func<TSender, IObservable<TRet>>> obs5, Expression<Func<TSender, IObservable<TRet>>> obs6, Expression<Func<TSender, IObservable<TRet>>> obs7, Expression<Func<TSender, IObservable<TRet>>> obs8)
-    where TSender : class
+                public static IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, Expression<Func<TSender, IObservable<TRet>?>> obs1, Expression<Func<TSender, IObservable<TRet>?>> obs2, Expression<Func<TSender, IObservable<TRet>?>> obs3, Expression<Func<TSender, IObservable<TRet>?>> obs4, Expression<Func<TSender, IObservable<TRet>?>> obs5, Expression<Func<TSender, IObservable<TRet>?>> obs6, Expression<Func<TSender, IObservable<TRet>?>> obs7, Expression<Func<TSender, IObservable<TRet>?>> obs8)
+            where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, (o1, o2, o3, o4, o5, o6, o7, o8) => new[] { o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull(), o6.Value.EmptyIfNull(), o7.Value.EmptyIfNull(), o8.Value.EmptyIfNull() })
-                .Select(x => x.Merge()).Switch();
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, (o1, o2, o3, o4, o5, o6, o7, o8) => new[] {o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull(), o6.Value!.EmptyIfNull(), o7.Value!.EmptyIfNull(), o8.Value!.EmptyIfNull()})
+                .Select(x => x?.Merge())!.Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
         /// <param name="sender">The object where the property chain starts.</param>
@@ -1672,11 +1674,11 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender se
         /// <param name="obs7">The 7 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs8">The 8 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs9">The 9 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, Expression<Func<TSender, IObservable<TRet>>> obs1, Expression<Func<TSender, IObservable<TRet>>> obs2, Expression<Func<TSender, IObservable<TRet>>> obs3, Expression<Func<TSender, IObservable<TRet>>> obs4, Expression<Func<TSender, IObservable<TRet>>> obs5, Expression<Func<TSender, IObservable<TRet>>> obs6, Expression<Func<TSender, IObservable<TRet>>> obs7, Expression<Func<TSender, IObservable<TRet>>> obs8, Expression<Func<TSender, IObservable<TRet>>> obs9)
-    where TSender : class
+                public static IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, Expression<Func<TSender, IObservable<TRet>?>> obs1, Expression<Func<TSender, IObservable<TRet>?>> obs2, Expression<Func<TSender, IObservable<TRet>?>> obs3, Expression<Func<TSender, IObservable<TRet>?>> obs4, Expression<Func<TSender, IObservable<TRet>?>> obs5, Expression<Func<TSender, IObservable<TRet>?>> obs6, Expression<Func<TSender, IObservable<TRet>?>> obs7, Expression<Func<TSender, IObservable<TRet>?>> obs8, Expression<Func<TSender, IObservable<TRet>?>> obs9)
+            where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, (o1, o2, o3, o4, o5, o6, o7, o8, o9) => new[] { o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull(), o6.Value.EmptyIfNull(), o7.Value.EmptyIfNull(), o8.Value.EmptyIfNull(), o9.Value.EmptyIfNull() })
-                .Select(x => x.Merge()).Switch();
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, (o1, o2, o3, o4, o5, o6, o7, o8, o9) => new[] {o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull(), o6.Value!.EmptyIfNull(), o7.Value!.EmptyIfNull(), o8.Value!.EmptyIfNull(), o9.Value!.EmptyIfNull()})
+                .Select(x => x?.Merge())!.Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
         /// <param name="sender">The object where the property chain starts.</param>
@@ -1690,11 +1692,11 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender se
         /// <param name="obs8">The 8 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs9">The 9 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs10">The 10 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, Expression<Func<TSender, IObservable<TRet>>> obs1, Expression<Func<TSender, IObservable<TRet>>> obs2, Expression<Func<TSender, IObservable<TRet>>> obs3, Expression<Func<TSender, IObservable<TRet>>> obs4, Expression<Func<TSender, IObservable<TRet>>> obs5, Expression<Func<TSender, IObservable<TRet>>> obs6, Expression<Func<TSender, IObservable<TRet>>> obs7, Expression<Func<TSender, IObservable<TRet>>> obs8, Expression<Func<TSender, IObservable<TRet>>> obs9, Expression<Func<TSender, IObservable<TRet>>> obs10)
-    where TSender : class
+                public static IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, Expression<Func<TSender, IObservable<TRet>?>> obs1, Expression<Func<TSender, IObservable<TRet>?>> obs2, Expression<Func<TSender, IObservable<TRet>?>> obs3, Expression<Func<TSender, IObservable<TRet>?>> obs4, Expression<Func<TSender, IObservable<TRet>?>> obs5, Expression<Func<TSender, IObservable<TRet>?>> obs6, Expression<Func<TSender, IObservable<TRet>?>> obs7, Expression<Func<TSender, IObservable<TRet>?>> obs8, Expression<Func<TSender, IObservable<TRet>?>> obs9, Expression<Func<TSender, IObservable<TRet>?>> obs10)
+            where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, obs10, (o1, o2, o3, o4, o5, o6, o7, o8, o9, o10) => new[] { o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull(), o6.Value.EmptyIfNull(), o7.Value.EmptyIfNull(), o8.Value.EmptyIfNull(), o9.Value.EmptyIfNull(), o10.Value.EmptyIfNull() })
-                .Select(x => x.Merge()).Switch();
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, obs10, (o1, o2, o3, o4, o5, o6, o7, o8, o9, o10) => new[] {o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull(), o6.Value!.EmptyIfNull(), o7.Value!.EmptyIfNull(), o8.Value!.EmptyIfNull(), o9.Value!.EmptyIfNull(), o10.Value!.EmptyIfNull()})
+                .Select(x => x?.Merge())!.Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
         /// <param name="sender">The object where the property chain starts.</param>
@@ -1709,11 +1711,11 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender se
         /// <param name="obs9">The 9 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs10">The 10 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs11">The 11 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, Expression<Func<TSender, IObservable<TRet>>> obs1, Expression<Func<TSender, IObservable<TRet>>> obs2, Expression<Func<TSender, IObservable<TRet>>> obs3, Expression<Func<TSender, IObservable<TRet>>> obs4, Expression<Func<TSender, IObservable<TRet>>> obs5, Expression<Func<TSender, IObservable<TRet>>> obs6, Expression<Func<TSender, IObservable<TRet>>> obs7, Expression<Func<TSender, IObservable<TRet>>> obs8, Expression<Func<TSender, IObservable<TRet>>> obs9, Expression<Func<TSender, IObservable<TRet>>> obs10, Expression<Func<TSender, IObservable<TRet>>> obs11)
-    where TSender : class
+                public static IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, Expression<Func<TSender, IObservable<TRet>?>> obs1, Expression<Func<TSender, IObservable<TRet>?>> obs2, Expression<Func<TSender, IObservable<TRet>?>> obs3, Expression<Func<TSender, IObservable<TRet>?>> obs4, Expression<Func<TSender, IObservable<TRet>?>> obs5, Expression<Func<TSender, IObservable<TRet>?>> obs6, Expression<Func<TSender, IObservable<TRet>?>> obs7, Expression<Func<TSender, IObservable<TRet>?>> obs8, Expression<Func<TSender, IObservable<TRet>?>> obs9, Expression<Func<TSender, IObservable<TRet>?>> obs10, Expression<Func<TSender, IObservable<TRet>?>> obs11)
+            where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, obs10, obs11, (o1, o2, o3, o4, o5, o6, o7, o8, o9, o10, o11) => new[] { o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull(), o6.Value.EmptyIfNull(), o7.Value.EmptyIfNull(), o8.Value.EmptyIfNull(), o9.Value.EmptyIfNull(), o10.Value.EmptyIfNull(), o11.Value.EmptyIfNull() })
-                .Select(x => x.Merge()).Switch();
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, obs10, obs11, (o1, o2, o3, o4, o5, o6, o7, o8, o9, o10, o11) => new[] {o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull(), o6.Value!.EmptyIfNull(), o7.Value!.EmptyIfNull(), o8.Value!.EmptyIfNull(), o9.Value!.EmptyIfNull(), o10.Value!.EmptyIfNull(), o11.Value!.EmptyIfNull()})
+                .Select(x => x?.Merge())!.Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
         /// <param name="sender">The object where the property chain starts.</param>
@@ -1729,11 +1731,11 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender se
         /// <param name="obs10">The 10 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs11">The 11 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         /// <param name="obs12">The 12 property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, Expression<Func<TSender, IObservable<TRet>>> obs1, Expression<Func<TSender, IObservable<TRet>>> obs2, Expression<Func<TSender, IObservable<TRet>>> obs3, Expression<Func<TSender, IObservable<TRet>>> obs4, Expression<Func<TSender, IObservable<TRet>>> obs5, Expression<Func<TSender, IObservable<TRet>>> obs6, Expression<Func<TSender, IObservable<TRet>>> obs7, Expression<Func<TSender, IObservable<TRet>>> obs8, Expression<Func<TSender, IObservable<TRet>>> obs9, Expression<Func<TSender, IObservable<TRet>>> obs10, Expression<Func<TSender, IObservable<TRet>>> obs11, Expression<Func<TSender, IObservable<TRet>>> obs12)
-    where TSender : class
+                public static IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, Expression<Func<TSender, IObservable<TRet>?>> obs1, Expression<Func<TSender, IObservable<TRet>?>> obs2, Expression<Func<TSender, IObservable<TRet>?>> obs3, Expression<Func<TSender, IObservable<TRet>?>> obs4, Expression<Func<TSender, IObservable<TRet>?>> obs5, Expression<Func<TSender, IObservable<TRet>?>> obs6, Expression<Func<TSender, IObservable<TRet>?>> obs7, Expression<Func<TSender, IObservable<TRet>?>> obs8, Expression<Func<TSender, IObservable<TRet>?>> obs9, Expression<Func<TSender, IObservable<TRet>?>> obs10, Expression<Func<TSender, IObservable<TRet>?>> obs11, Expression<Func<TSender, IObservable<TRet>?>> obs12)
+            where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, obs10, obs11, obs12, (o1, o2, o3, o4, o5, o6, o7, o8, o9, o10, o11, o12) => new[] { o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull(), o6.Value.EmptyIfNull(), o7.Value.EmptyIfNull(), o8.Value.EmptyIfNull(), o9.Value.EmptyIfNull(), o10.Value.EmptyIfNull(), o11.Value.EmptyIfNull(), o12.Value.EmptyIfNull() })
-                .Select(x => x.Merge()).Switch();
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, obs10, obs11, obs12, (o1, o2, o3, o4, o5, o6, o7, o8, o9, o10, o11, o12) => new[] {o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull(), o6.Value!.EmptyIfNull(), o7.Value!.EmptyIfNull(), o8.Value!.EmptyIfNull(), o9.Value!.EmptyIfNull(), o10.Value!.EmptyIfNull(), o11.Value!.EmptyIfNull(), o12.Value!.EmptyIfNull()})
+                .Select(x => x?.Merge())!.Switch();
         }
 
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
@@ -1741,13 +1743,13 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender se
         /// <param name="obs1">The 1 property chain to reference.</param>
         /// <param name="obs2">The 2 property chain to reference.</param>
         /// <param name="selector">The selector which will determine the final value from the properties. This must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2>(this TSender sender,
-                            Expression<Func<TSender, IObservable<T1>>> obs1,
-                            Expression<Func<TSender, IObservable<T2>>> obs2,
-                            Func<T1, T2, TRet> selector)
+        public static IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1,T2>(this TSender? sender,
+                            Expression<Func<TSender, IObservable<T1>?>> obs1,
+                            Expression<Func<TSender, IObservable<T2>?>> obs2,
+                            Func<T1?, T2?, TRet?> selector)
             where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, (o1, o2) => Observable.CombineLatest(o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), selector))
+            return sender!.WhenAny(obs1, obs2, (o1, o2) => Observable.CombineLatest(o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), selector))!
                 .Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
@@ -1756,14 +1758,14 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2>(this TS
         /// <param name="obs2">The 2 property chain to reference.</param>
         /// <param name="obs3">The 3 property chain to reference.</param>
         /// <param name="selector">The selector which will determine the final value from the properties. This must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3>(this TSender sender,
-                            Expression<Func<TSender, IObservable<T1>>> obs1,
-                            Expression<Func<TSender, IObservable<T2>>> obs2,
-                            Expression<Func<TSender, IObservable<T3>>> obs3,
-                            Func<T1, T2, T3, TRet> selector)
+        public static IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1,T2,T3>(this TSender? sender,
+                            Expression<Func<TSender, IObservable<T1>?>> obs1,
+                            Expression<Func<TSender, IObservable<T2>?>> obs2,
+                            Expression<Func<TSender, IObservable<T3>?>> obs3,
+                            Func<T1?, T2?, T3?, TRet?> selector)
             where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, (o1, o2, o3) => Observable.CombineLatest(o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), selector))
+            return sender!.WhenAny(obs1, obs2, obs3, (o1, o2, o3) => Observable.CombineLatest(o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), selector))!
                 .Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
@@ -1773,15 +1775,15 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3>(thi
         /// <param name="obs3">The 3 property chain to reference.</param>
         /// <param name="obs4">The 4 property chain to reference.</param>
         /// <param name="selector">The selector which will determine the final value from the properties. This must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4>(this TSender sender,
-                            Expression<Func<TSender, IObservable<T1>>> obs1,
-                            Expression<Func<TSender, IObservable<T2>>> obs2,
-                            Expression<Func<TSender, IObservable<T3>>> obs3,
-                            Expression<Func<TSender, IObservable<T4>>> obs4,
-                            Func<T1, T2, T3, T4, TRet> selector)
+        public static IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1,T2,T3,T4>(this TSender? sender,
+                            Expression<Func<TSender, IObservable<T1>?>> obs1,
+                            Expression<Func<TSender, IObservable<T2>?>> obs2,
+                            Expression<Func<TSender, IObservable<T3>?>> obs3,
+                            Expression<Func<TSender, IObservable<T4>?>> obs4,
+                            Func<T1?, T2?, T3?, T4?, TRet?> selector)
             where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, (o1, o2, o3, o4) => Observable.CombineLatest(o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), selector))
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, (o1, o2, o3, o4) => Observable.CombineLatest(o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), selector))!
                 .Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
@@ -1792,16 +1794,16 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4>
         /// <param name="obs4">The 4 property chain to reference.</param>
         /// <param name="obs5">The 5 property chain to reference.</param>
         /// <param name="selector">The selector which will determine the final value from the properties. This must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5>(this TSender sender,
-                            Expression<Func<TSender, IObservable<T1>>> obs1,
-                            Expression<Func<TSender, IObservable<T2>>> obs2,
-                            Expression<Func<TSender, IObservable<T3>>> obs3,
-                            Expression<Func<TSender, IObservable<T4>>> obs4,
-                            Expression<Func<TSender, IObservable<T5>>> obs5,
-                            Func<T1, T2, T3, T4, T5, TRet> selector)
+        public static IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1,T2,T3,T4,T5>(this TSender? sender,
+                            Expression<Func<TSender, IObservable<T1>?>> obs1,
+                            Expression<Func<TSender, IObservable<T2>?>> obs2,
+                            Expression<Func<TSender, IObservable<T3>?>> obs3,
+                            Expression<Func<TSender, IObservable<T4>?>> obs4,
+                            Expression<Func<TSender, IObservable<T5>?>> obs5,
+                            Func<T1?, T2?, T3?, T4?, T5?, TRet?> selector)
             where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, (o1, o2, o3, o4, o5) => Observable.CombineLatest(o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull(), selector))
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, (o1, o2, o3, o4, o5) => Observable.CombineLatest(o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull(), selector))!
                 .Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
@@ -1813,17 +1815,17 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4,
         /// <param name="obs5">The 5 property chain to reference.</param>
         /// <param name="obs6">The 6 property chain to reference.</param>
         /// <param name="selector">The selector which will determine the final value from the properties. This must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6>(this TSender sender,
-                            Expression<Func<TSender, IObservable<T1>>> obs1,
-                            Expression<Func<TSender, IObservable<T2>>> obs2,
-                            Expression<Func<TSender, IObservable<T3>>> obs3,
-                            Expression<Func<TSender, IObservable<T4>>> obs4,
-                            Expression<Func<TSender, IObservable<T5>>> obs5,
-                            Expression<Func<TSender, IObservable<T6>>> obs6,
-                            Func<T1, T2, T3, T4, T5, T6, TRet> selector)
+        public static IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1,T2,T3,T4,T5,T6>(this TSender? sender,
+                            Expression<Func<TSender, IObservable<T1>?>> obs1,
+                            Expression<Func<TSender, IObservable<T2>?>> obs2,
+                            Expression<Func<TSender, IObservable<T3>?>> obs3,
+                            Expression<Func<TSender, IObservable<T4>?>> obs4,
+                            Expression<Func<TSender, IObservable<T5>?>> obs5,
+                            Expression<Func<TSender, IObservable<T6>?>> obs6,
+                            Func<T1?, T2?, T3?, T4?, T5?, T6?, TRet?> selector)
             where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, (o1, o2, o3, o4, o5, o6) => Observable.CombineLatest(o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull(), o6.Value.EmptyIfNull(), selector))
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, (o1, o2, o3, o4, o5, o6) => Observable.CombineLatest(o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull(), o6.Value!.EmptyIfNull(), selector))!
                 .Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
@@ -1836,18 +1838,18 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4,
         /// <param name="obs6">The 6 property chain to reference.</param>
         /// <param name="obs7">The 7 property chain to reference.</param>
         /// <param name="selector">The selector which will determine the final value from the properties. This must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7>(this TSender sender,
-                            Expression<Func<TSender, IObservable<T1>>> obs1,
-                            Expression<Func<TSender, IObservable<T2>>> obs2,
-                            Expression<Func<TSender, IObservable<T3>>> obs3,
-                            Expression<Func<TSender, IObservable<T4>>> obs4,
-                            Expression<Func<TSender, IObservable<T5>>> obs5,
-                            Expression<Func<TSender, IObservable<T6>>> obs6,
-                            Expression<Func<TSender, IObservable<T7>>> obs7,
-                            Func<T1, T2, T3, T4, T5, T6, T7, TRet> selector)
+        public static IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1,T2,T3,T4,T5,T6,T7>(this TSender? sender,
+                            Expression<Func<TSender, IObservable<T1>?>> obs1,
+                            Expression<Func<TSender, IObservable<T2>?>> obs2,
+                            Expression<Func<TSender, IObservable<T3>?>> obs3,
+                            Expression<Func<TSender, IObservable<T4>?>> obs4,
+                            Expression<Func<TSender, IObservable<T5>?>> obs5,
+                            Expression<Func<TSender, IObservable<T6>?>> obs6,
+                            Expression<Func<TSender, IObservable<T7>?>> obs7,
+                            Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, TRet?> selector)
             where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, (o1, o2, o3, o4, o5, o6, o7) => Observable.CombineLatest(o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull(), o6.Value.EmptyIfNull(), o7.Value.EmptyIfNull(), selector))
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, (o1, o2, o3, o4, o5, o6, o7) => Observable.CombineLatest(o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull(), o6.Value!.EmptyIfNull(), o7.Value!.EmptyIfNull(), selector))!
                 .Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
@@ -1861,19 +1863,19 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4,
         /// <param name="obs7">The 7 property chain to reference.</param>
         /// <param name="obs8">The 8 property chain to reference.</param>
         /// <param name="selector">The selector which will determine the final value from the properties. This must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8>(this TSender sender,
-                            Expression<Func<TSender, IObservable<T1>>> obs1,
-                            Expression<Func<TSender, IObservable<T2>>> obs2,
-                            Expression<Func<TSender, IObservable<T3>>> obs3,
-                            Expression<Func<TSender, IObservable<T4>>> obs4,
-                            Expression<Func<TSender, IObservable<T5>>> obs5,
-                            Expression<Func<TSender, IObservable<T6>>> obs6,
-                            Expression<Func<TSender, IObservable<T7>>> obs7,
-                            Expression<Func<TSender, IObservable<T8>>> obs8,
-                            Func<T1, T2, T3, T4, T5, T6, T7, T8, TRet> selector)
+        public static IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1,T2,T3,T4,T5,T6,T7,T8>(this TSender? sender,
+                            Expression<Func<TSender, IObservable<T1>?>> obs1,
+                            Expression<Func<TSender, IObservable<T2>?>> obs2,
+                            Expression<Func<TSender, IObservable<T3>?>> obs3,
+                            Expression<Func<TSender, IObservable<T4>?>> obs4,
+                            Expression<Func<TSender, IObservable<T5>?>> obs5,
+                            Expression<Func<TSender, IObservable<T6>?>> obs6,
+                            Expression<Func<TSender, IObservable<T7>?>> obs7,
+                            Expression<Func<TSender, IObservable<T8>?>> obs8,
+                            Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, TRet?> selector)
             where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, (o1, o2, o3, o4, o5, o6, o7, o8) => Observable.CombineLatest(o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull(), o6.Value.EmptyIfNull(), o7.Value.EmptyIfNull(), o8.Value.EmptyIfNull(), selector))
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, (o1, o2, o3, o4, o5, o6, o7, o8) => Observable.CombineLatest(o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull(), o6.Value!.EmptyIfNull(), o7.Value!.EmptyIfNull(), o8.Value!.EmptyIfNull(), selector))!
                 .Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
@@ -1888,20 +1890,20 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4,
         /// <param name="obs8">The 8 property chain to reference.</param>
         /// <param name="obs9">The 9 property chain to reference.</param>
         /// <param name="selector">The selector which will determine the final value from the properties. This must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9>(this TSender sender,
-                            Expression<Func<TSender, IObservable<T1>>> obs1,
-                            Expression<Func<TSender, IObservable<T2>>> obs2,
-                            Expression<Func<TSender, IObservable<T3>>> obs3,
-                            Expression<Func<TSender, IObservable<T4>>> obs4,
-                            Expression<Func<TSender, IObservable<T5>>> obs5,
-                            Expression<Func<TSender, IObservable<T6>>> obs6,
-                            Expression<Func<TSender, IObservable<T7>>> obs7,
-                            Expression<Func<TSender, IObservable<T8>>> obs8,
-                            Expression<Func<TSender, IObservable<T9>>> obs9,
-                            Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, TRet> selector)
+        public static IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1,T2,T3,T4,T5,T6,T7,T8,T9>(this TSender? sender,
+                            Expression<Func<TSender, IObservable<T1>?>> obs1,
+                            Expression<Func<TSender, IObservable<T2>?>> obs2,
+                            Expression<Func<TSender, IObservable<T3>?>> obs3,
+                            Expression<Func<TSender, IObservable<T4>?>> obs4,
+                            Expression<Func<TSender, IObservable<T5>?>> obs5,
+                            Expression<Func<TSender, IObservable<T6>?>> obs6,
+                            Expression<Func<TSender, IObservable<T7>?>> obs7,
+                            Expression<Func<TSender, IObservable<T8>?>> obs8,
+                            Expression<Func<TSender, IObservable<T9>?>> obs9,
+                            Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, TRet?> selector)
             where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, (o1, o2, o3, o4, o5, o6, o7, o8, o9) => Observable.CombineLatest(o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull(), o6.Value.EmptyIfNull(), o7.Value.EmptyIfNull(), o8.Value.EmptyIfNull(), o9.Value.EmptyIfNull(), selector))
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, (o1, o2, o3, o4, o5, o6, o7, o8, o9) => Observable.CombineLatest(o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull(), o6.Value!.EmptyIfNull(), o7.Value!.EmptyIfNull(), o8.Value!.EmptyIfNull(), o9.Value!.EmptyIfNull(), selector))!
                 .Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
@@ -1917,21 +1919,21 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4,
         /// <param name="obs9">The 9 property chain to reference.</param>
         /// <param name="obs10">The 10 property chain to reference.</param>
         /// <param name="selector">The selector which will determine the final value from the properties. This must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this TSender sender,
-                            Expression<Func<TSender, IObservable<T1>>> obs1,
-                            Expression<Func<TSender, IObservable<T2>>> obs2,
-                            Expression<Func<TSender, IObservable<T3>>> obs3,
-                            Expression<Func<TSender, IObservable<T4>>> obs4,
-                            Expression<Func<TSender, IObservable<T5>>> obs5,
-                            Expression<Func<TSender, IObservable<T6>>> obs6,
-                            Expression<Func<TSender, IObservable<T7>>> obs7,
-                            Expression<Func<TSender, IObservable<T8>>> obs8,
-                            Expression<Func<TSender, IObservable<T9>>> obs9,
-                            Expression<Func<TSender, IObservable<T10>>> obs10,
-                            Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TRet> selector)
+        public static IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1,T2,T3,T4,T5,T6,T7,T8,T9,T10>(this TSender? sender,
+                            Expression<Func<TSender, IObservable<T1>?>> obs1,
+                            Expression<Func<TSender, IObservable<T2>?>> obs2,
+                            Expression<Func<TSender, IObservable<T3>?>> obs3,
+                            Expression<Func<TSender, IObservable<T4>?>> obs4,
+                            Expression<Func<TSender, IObservable<T5>?>> obs5,
+                            Expression<Func<TSender, IObservable<T6>?>> obs6,
+                            Expression<Func<TSender, IObservable<T7>?>> obs7,
+                            Expression<Func<TSender, IObservable<T8>?>> obs8,
+                            Expression<Func<TSender, IObservable<T9>?>> obs9,
+                            Expression<Func<TSender, IObservable<T10>?>> obs10,
+                            Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, TRet?> selector)
             where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, obs10, (o1, o2, o3, o4, o5, o6, o7, o8, o9, o10) => Observable.CombineLatest(o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull(), o6.Value.EmptyIfNull(), o7.Value.EmptyIfNull(), o8.Value.EmptyIfNull(), o9.Value.EmptyIfNull(), o10.Value.EmptyIfNull(), selector))
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, obs10, (o1, o2, o3, o4, o5, o6, o7, o8, o9, o10) => Observable.CombineLatest(o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull(), o6.Value!.EmptyIfNull(), o7.Value!.EmptyIfNull(), o8.Value!.EmptyIfNull(), o9.Value!.EmptyIfNull(), o10.Value!.EmptyIfNull(), selector))!
                 .Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
@@ -1948,22 +1950,22 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4,
         /// <param name="obs10">The 10 property chain to reference.</param>
         /// <param name="obs11">The 11 property chain to reference.</param>
         /// <param name="selector">The selector which will determine the final value from the properties. This must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this TSender sender,
-                            Expression<Func<TSender, IObservable<T1>>> obs1,
-                            Expression<Func<TSender, IObservable<T2>>> obs2,
-                            Expression<Func<TSender, IObservable<T3>>> obs3,
-                            Expression<Func<TSender, IObservable<T4>>> obs4,
-                            Expression<Func<TSender, IObservable<T5>>> obs5,
-                            Expression<Func<TSender, IObservable<T6>>> obs6,
-                            Expression<Func<TSender, IObservable<T7>>> obs7,
-                            Expression<Func<TSender, IObservable<T8>>> obs8,
-                            Expression<Func<TSender, IObservable<T9>>> obs9,
-                            Expression<Func<TSender, IObservable<T10>>> obs10,
-                            Expression<Func<TSender, IObservable<T11>>> obs11,
-                            Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, TRet> selector)
+        public static IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11>(this TSender? sender,
+                            Expression<Func<TSender, IObservable<T1>?>> obs1,
+                            Expression<Func<TSender, IObservable<T2>?>> obs2,
+                            Expression<Func<TSender, IObservable<T3>?>> obs3,
+                            Expression<Func<TSender, IObservable<T4>?>> obs4,
+                            Expression<Func<TSender, IObservable<T5>?>> obs5,
+                            Expression<Func<TSender, IObservable<T6>?>> obs6,
+                            Expression<Func<TSender, IObservable<T7>?>> obs7,
+                            Expression<Func<TSender, IObservable<T8>?>> obs8,
+                            Expression<Func<TSender, IObservable<T9>?>> obs9,
+                            Expression<Func<TSender, IObservable<T10>?>> obs10,
+                            Expression<Func<TSender, IObservable<T11>?>> obs11,
+                            Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, TRet?> selector)
             where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, obs10, obs11, (o1, o2, o3, o4, o5, o6, o7, o8, o9, o10, o11) => Observable.CombineLatest(o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull(), o6.Value.EmptyIfNull(), o7.Value.EmptyIfNull(), o8.Value.EmptyIfNull(), o9.Value.EmptyIfNull(), o10.Value.EmptyIfNull(), o11.Value.EmptyIfNull(), selector))
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, obs10, obs11, (o1, o2, o3, o4, o5, o6, o7, o8, o9, o10, o11) => Observable.CombineLatest(o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull(), o6.Value!.EmptyIfNull(), o7.Value!.EmptyIfNull(), o8.Value!.EmptyIfNull(), o9.Value!.EmptyIfNull(), o10.Value!.EmptyIfNull(), o11.Value!.EmptyIfNull(), selector))!
                 .Switch();
         }
         /// <summary>Monitor a property that is an observable, and subscribe to the most recent emitted value.</summary>
@@ -1981,26 +1983,26 @@ public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4,
         /// <param name="obs11">The 11 property chain to reference.</param>
         /// <param name="obs12">The 12 property chain to reference.</param>
         /// <param name="selector">The selector which will determine the final value from the properties. This must be an observable.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this TSender sender,
-                            Expression<Func<TSender, IObservable<T1>>> obs1,
-                            Expression<Func<TSender, IObservable<T2>>> obs2,
-                            Expression<Func<TSender, IObservable<T3>>> obs3,
-                            Expression<Func<TSender, IObservable<T4>>> obs4,
-                            Expression<Func<TSender, IObservable<T5>>> obs5,
-                            Expression<Func<TSender, IObservable<T6>>> obs6,
-                            Expression<Func<TSender, IObservable<T7>>> obs7,
-                            Expression<Func<TSender, IObservable<T8>>> obs8,
-                            Expression<Func<TSender, IObservable<T9>>> obs9,
-                            Expression<Func<TSender, IObservable<T10>>> obs10,
-                            Expression<Func<TSender, IObservable<T11>>> obs11,
-                            Expression<Func<TSender, IObservable<T12>>> obs12,
-                            Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, TRet> selector)
+        public static IObservable<TRet?> WhenAnyObservable<TSender, TRet, T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12>(this TSender? sender,
+                            Expression<Func<TSender, IObservable<T1>?>> obs1,
+                            Expression<Func<TSender, IObservable<T2>?>> obs2,
+                            Expression<Func<TSender, IObservable<T3>?>> obs3,
+                            Expression<Func<TSender, IObservable<T4>?>> obs4,
+                            Expression<Func<TSender, IObservable<T5>?>> obs5,
+                            Expression<Func<TSender, IObservable<T6>?>> obs6,
+                            Expression<Func<TSender, IObservable<T7>?>> obs7,
+                            Expression<Func<TSender, IObservable<T8>?>> obs8,
+                            Expression<Func<TSender, IObservable<T9>?>> obs9,
+                            Expression<Func<TSender, IObservable<T10>?>> obs10,
+                            Expression<Func<TSender, IObservable<T11>?>> obs11,
+                            Expression<Func<TSender, IObservable<T12>?>> obs12,
+                            Func<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, TRet?> selector)
             where TSender : class
         {
-            return sender.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, obs10, obs11, obs12, (o1, o2, o3, o4, o5, o6, o7, o8, o9, o10, o11, o12) => Observable.CombineLatest(o1.Value.EmptyIfNull(), o2.Value.EmptyIfNull(), o3.Value.EmptyIfNull(), o4.Value.EmptyIfNull(), o5.Value.EmptyIfNull(), o6.Value.EmptyIfNull(), o7.Value.EmptyIfNull(), o8.Value.EmptyIfNull(), o9.Value.EmptyIfNull(), o10.Value.EmptyIfNull(), o11.Value.EmptyIfNull(), o12.Value.EmptyIfNull(), selector))
+            return sender!.WhenAny(obs1, obs2, obs3, obs4, obs5, obs6, obs7, obs8, obs9, obs10, obs11, obs12, (o1, o2, o3, o4, o5, o6, o7, o8, o9, o10, o11, o12) => Observable.CombineLatest(o1.Value!.EmptyIfNull(), o2.Value!.EmptyIfNull(), o3.Value!.EmptyIfNull(), o4.Value!.EmptyIfNull(), o5.Value!.EmptyIfNull(), o6.Value!.EmptyIfNull(), o7.Value!.EmptyIfNull(), o8.Value!.EmptyIfNull(), o9.Value!.EmptyIfNull(), o10.Value!.EmptyIfNull(), o11.Value!.EmptyIfNull(), o12.Value!.EmptyIfNull(), selector))!
                 .Switch();
         }
-    }
+}
 
     internal static class ObservableExtensions
     {
diff --git a/src/ReactiveUI/VariadicTemplates.tt b/src/ReactiveUI/VariadicTemplates.tt
index 4745aa02d9..57c87ab51d 100644
--- a/src/ReactiveUI/VariadicTemplates.tt
+++ b/src/ReactiveUI/VariadicTemplates.tt
@@ -6,6 +6,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 //------------------------------------------------------------------------------
 // <auto-generated>
 //    This code was generated from a template.
@@ -42,20 +44,21 @@ namespace ReactiveUI
         /// </summary>
         /// <param name="sender">The object where the property chain starts.</param>
         /// <param name="property1">The first property chain to reference. This will be a expression pointing to a end property or field.</param>
-        public static IObservable<TRet> WhenAnyValue<TSender, TRet>(
-            this TSender sender,
-            Expression<Func<TSender, TRet>> property1)
+        public static IObservable<TRet?> WhenAnyValue<TSender, TRet>(
+            this TSender? sender,
+            Expression<Func<TSender, TRet?>> property1)
         {
-            return sender.WhenAny(property1, (IObservedChange<TSender, TRet> c1) => c1.Value);
+            return sender.WhenAny(property1, (IObservedChange<TSender, TRet?> c1) => c1.Value);
         }
 
         <# for(int length=1; length <= maxFuncLength; length++) { #>
-        <# var templParams = Enumerable.Range(1, length).Select(x => "T" + x.ToString()); #>
+        <# var templParams = Enumerable.Range(1, length).Select(x => "T" + x.ToString() + "?"); #>
+        <# var templParamsDec = Enumerable.Range(1, length).Select(x => "T" + x.ToString()); #>
         <# string selectorTypeParams = String.Join(", ", templParams.Select(x => String.Format("IObservedChange<TSender, {0}>", x))); #>
         <# string valuePropertyParams = String.Join(", ", Enumerable.Range(1, length).Select(x => String.Format("property{0}", x))); #>
         <# string valueSelectorParams = String.Join(", ", Enumerable.Range(1, length).Select(x => "c" + x)); #>
         <# string valueSelectorArgs = String.Join(", ", Enumerable.Range(1, length).Select(x => String.Format("c{0}.Value", x))); #>
-        <# string dynamicSelectorTypeParams = String.Join(", ", templParams.Select(x => "IObservedChange<TSender, object>")); #>
+        <# string dynamicSelectorTypeParams = String.Join(", ", templParams.Select(x => "IObservedChange<TSender?, object?>")); #>
         <# string selectorCall = "selector(" + String.Join(", ", Enumerable.Range(1, length).Select(x => "islot" + x.ToString())) + ")"; #>
 
         <# if (length != 1 && length <= 7) { #>/// <summary>
@@ -68,10 +71,10 @@ namespace ReactiveUI
         /// <param name="sender">The object where the property chain starts.</param>
         <# for(int i=1; i <= length; i++) { #>
 /// <param name="property<#=i#>">The <#=i#> property chain to reference. This will be a expression pointing to a end property or field.</param>
-        <# } #>public static IObservable<(<#= String.Join(",", templParams) #>)> WhenAnyValue<TSender, <#= String.Join(",", templParams) #>>(
-            this TSender sender,
+        <# } #>public static IObservable<(<#= String.Join(",", templParams) #>)> WhenAnyValue<TSender, <#= String.Join(",", templParamsDec) #>>(
+            this TSender? sender,
             <# for(int i=1; i <= length; i++) { #>
-            Expression<Func<TSender, T<#=i#>>> property<#=i#><# if (i != length) { #>,<# } #>
+            Expression<Func<TSender, T<#=i#>?>> property<#=i#><# if (i != length) { #>,<# } #>
 
             <# } #>)
         {
@@ -92,10 +95,10 @@ namespace ReactiveUI
         <# for(int i=1; i <= length; i++) { #>
 /// <param name="property<#=i#>">The <#=i#> property chain to reference. This will be a expression pointing to a end property or field.</param>
         <# } #>/// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyValue<TSender, TRet, <#= String.Join(",", templParams) #>>(
-            this TSender sender,
+        public static IObservable<TRet?> WhenAnyValue<TSender, TRet, <#= String.Join(",", templParamsDec) #>>(
+            this TSender? sender,
             <# for(int i=1; i <= length; i++) { #>
-            Expression<Func<TSender, T<#=i#>>> property<#=i#>,
+            Expression<Func<TSender, T<#=i#>?>> property<#=i#>,
             <# } #>
             Func<<#= String.Join(",", templParams) #>, TRet> selector)
         {
@@ -115,12 +118,12 @@ namespace ReactiveUI
         <# for(int i=1; i <= length; i++) { #>
 /// <param name="property<#=i#>">The <#=i#> property chain to reference. This will be a expression pointing to a end property or field.</param>
         <# } #>/// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAny<TSender, TRet, <#= String.Join(",", templParams) #>>(
-                this TSender sender,
+        public static IObservable<TRet?> WhenAny<TSender, TRet, <#= String.Join(",", templParamsDec) #>>(
+                this TSender? sender,
             <# for(int i=1; i <= length; i++) { #>
-                Expression<Func<TSender, T<#=i#>>> property<#=i#>,
+                Expression<Func<TSender, T<#=i#>?>> property<#=i#>,
             <# } #>
-                Func<<#= selectorTypeParams #>, TRet> selector)
+                Func<<#= selectorTypeParams #>, TRet?> selector)
         {
             <# if (length == 1){ #>
                 return sender.ObservableForProperty(property<#=1#>, false, false).Select(selector);
@@ -146,21 +149,21 @@ namespace ReactiveUI
         <# for(int i=1; i <= length; i++) { #>
 /// <param name="property<#=i#>">The <#=i#> property chain to reference. This will be a expression pointing to a end property or field.</param>
         <# } #>/// <param name="selector">The selector which will determine the final value from the properties.</param>
-        public static IObservable<TRet> WhenAnyDynamic<TSender, TRet>(
-                this TSender sender,
+        public static IObservable<TRet?> WhenAnyDynamic<TSender, TRet>(
+                this TSender? sender,
             <# for(int i=1; i <= length; i++) { #>
-                Expression property<#=i#>,
+                Expression? property<#=i#>,
             <# } #>
-                Func<<#= dynamicSelectorTypeParams #>, TRet> selector)
+                Func<<#= dynamicSelectorTypeParams #>, TRet?> selector)
         {
             <# if (length == 1){ #>
                 return ReactiveNotifyPropertyChangedMixin
-                    .SubscribeToExpressionChain<TSender,object>(sender, property<#=1#>, false, false).Select(selector);
+                    .SubscribeToExpressionChain<TSender,object?>(sender, property<#=1#>, false, false).Select(selector);
             <# }else{ #>
             return Observable.CombineLatest(
                 <# for(int i=1; i <= length; i++) { #>
                     ReactiveNotifyPropertyChangedMixin
-                        .SubscribeToExpressionChain<TSender,object>(sender, property<#=i#>, false, false),
+                        .SubscribeToExpressionChain<TSender,object?>(sender, property<#=i#>, false, false),
                 <# } #>
                 selector
             );
@@ -175,10 +178,10 @@ namespace ReactiveUI
         /// <summary>Observe a observable which is set to a property, and automatically subscribe to the most recent emitted value.</summary>
         /// <param name="sender">The object where the property chain starts.</param>
         /// <param name="obs1">The first observable to observe.</param>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, Expression<Func<TSender, IObservable<TRet>>> obs1)
+        public static IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, Expression<Func<TSender, IObservable<TRet>?>> obs1)
             where TSender : class
         {
-            return sender.WhenAny(obs1, x => x.Value.EmptyIfNull()).Switch();
+            return sender!.WhenAny(obs1, x => x.Value!.EmptyIfNull())!.Switch();
         }
 
 <# for(int length=2; length <= maxFuncLength; length++) { #>
@@ -187,14 +190,14 @@ namespace ReactiveUI
         <# for(int i=1; i <= length; i++) { #>
 /// <param name="obs<#=i#>">The <#=i#> property chain to reference which ends with an observable. This will be a expression pointing to a end property or field which must be an observable.</param>
         <# } #>
-<# string paramsStr = String.Join(", ", Enumerable.Range(1, length).Select(x => "Expression<Func<TSender, IObservable<TRet>>> obs" + x.ToString())); #>
+<# string paramsStr = String.Join(", ", Enumerable.Range(1, length).Select(x => "Expression<Func<TSender, IObservable<TRet>?>> obs" + x.ToString())); #>
 <# string varsStr = String.Join(", ", Enumerable.Range(1, length).Select(x => "obs" + x.ToString())); #>
-<# string valsStr = String.Join(", ", Enumerable.Range(1, length).Select(x => "o" + x.ToString() + ".Value.EmptyIfNull()")); #>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet>(this TSender sender, <#= paramsStr #>)
+<# string valsStr = String.Join(", ", Enumerable.Range(1, length).Select(x => "o" + x.ToString() + ".Value!.EmptyIfNull()")); #>
+        public static IObservable<TRet?> WhenAnyObservable<TSender, TRet>(this TSender? sender, <#= paramsStr #>)
             where TSender : class
         {
-            return sender.WhenAny(<#= varsStr #>, (<#=varsStr.Replace("obs", "o")#>) => new[] {<#= valsStr #>})
-                .Select(x => x.Merge()).Switch();
+            return sender!.WhenAny(<#= varsStr #>, (<#=varsStr.Replace("obs", "o")#>) => new[] {<#= valsStr #>})
+                .Select(x => x?.Merge())!.Switch();
         }
 <# } #>
 
@@ -204,18 +207,19 @@ namespace ReactiveUI
         <# for(int i=1; i <= length; i++) { #>
 /// <param name="obs<#=i#>">The <#=i#> property chain to reference.</param>
         <# } #>/// <param name="selector">The selector which will determine the final value from the properties. This must be an observable.</param>
-<# var templParams = Enumerable.Range(1, length).Select(x => "T" + x.ToString()); #>
+<# var templParams = Enumerable.Range(1, length).Select(x => "T" + x.ToString() + "?"); #>
+<# var templParamsDec = Enumerable.Range(1, length).Select(x => "T" + x.ToString()); #>
 <# string varsStr = String.Join(", ", Enumerable.Range(1, length).Select(x => "obs" + x.ToString())); #>
-<# string valsStr = String.Join(", ", Enumerable.Range(1, length).Select(x => "o" + x.ToString() + ".Value.EmptyIfNull()")); #>
+<# string valsStr = String.Join(", ", Enumerable.Range(1, length).Select(x => "o" + x.ToString() + ".Value!.EmptyIfNull()")); #>
 <# string selectorTypeParams = String.Join(", ", templParams); #>
-        public static IObservable<TRet> WhenAnyObservable<TSender, TRet, <#= String.Join(",", templParams) #>>(this TSender sender,
+        public static IObservable<TRet?> WhenAnyObservable<TSender, TRet, <#= String.Join(",", templParamsDec) #>>(this TSender? sender,
             <# for(int i=1; i <= length; i++) { #>
-                Expression<Func<TSender, IObservable<T<#=i#>>>> obs<#=i#>,
+                Expression<Func<TSender, IObservable<T<#=i#>>?>> obs<#=i#>,
             <# } #>
-                Func<<#= selectorTypeParams #>, TRet> selector)
+                Func<<#= selectorTypeParams #>, TRet?> selector)
             where TSender : class
         {
-            return sender.WhenAny(<#= varsStr #>, (<#=varsStr.Replace("obs", "o")#>) => Observable.CombineLatest(<#= valsStr #>, selector))
+            return sender!.WhenAny(<#= varsStr #>, (<#=varsStr.Replace("obs", "o")#>) => Observable.CombineLatest(<#= valsStr #>, selector))!
                 .Switch();
         }
 <# } #>