Remove obsolete MauiWinUIApplication properties (#17667)

* Remove obsolete MauiWinUIApplication properties

* - add better comments

* - ignore banned on winui generated xaml file

.editorconfig

@@ -184,3 +184,8 @@ indent_size = 2
 end_of_line = lf
 [*.{cmd, bat}]
 end_of_line = crlf
+
+# Ignore Banned APIs that get generated by the WinUI Xaml Generator
+# This is currently being used for the banned Services/Application APIs
+[**/obj/**/XamlTypeInfo.g.cs]
+dotnet_diagnostic.RS0030.severity = none

eng/BannedSymbols.txt

@@ -1,2 +1,4 @@
 M:Microsoft.Extensions.DependencyInjection.Extensions.ServiceCollectionDescriptorExtensions.TryAddSingleton`2(Microsoft.Extensions.DependencyInjection.IServiceCollection);Use a Factory method to create the service instead
 M:Android.Content.Res.ColorStateList.#ctor(System.Int32[][],System.Int32[]);Use Microsoft.Maui.PlatformInterop.Get*ColorStateList() Java methods instead
+P:Microsoft.Maui.MauiWinUIApplication.Services;Use the IPlatformApplication.Current.Services instead
+P:Microsoft.Maui.MauiWinUIApplication.Application;Use the IPlatformApplication.Current.Application instead

src/Core/src/Platform/Windows/MauiWinUIApplication.cs

@@ -61,14 +61,24 @@ protected override void OnLaunched(UI.Xaml.LaunchActivatedEventArgs args)
 
 		IApplication IPlatformApplication.Application => _application!;
 
-		[Obsolete("Use the IPlatformApplication.Current.Services instead.")]
+		// TODO NET9 MARK THESE AS OBSOLETE. We didn't mark them obsolete in NET8 because that
+		// was causing warnings to generate for our WinUI projects, so we need to workaround that
+		// before we mark this as obsolete.
+		/// <summary>
+		/// Use the IPlatformApplication.Current.Services instead.
+		/// </summary>
 		public IServiceProvider Services
 		{
 			get => _services!;
 			protected set => _services = value;
 		}
 
-		[Obsolete("Use the IPlatformApplication.Current.Application instead.")]
+		// TODO NET9 MARK THESE AS OBSOLETE. We didn't mark them obsolete in NET8 because that
+		// was causing warnings to generate for our WinUI projects, so we need to workaround that
+		// before we mark this as obsolete.
+		/// <summary>
+		/// Use the IPlatformApplication.Current.Application instead.
+		/// </summary>
 		public IApplication Application
 		{
 			get => _application!;