Add a WeakEventSource

TomsToolbox.Core/TomsToolbox.Core.ExternalAnnotations.xml

@@ -721,6 +721,16 @@
       <attribute ctor="M:JetBrains.Annotations.NotNullAttribute.#ctor" />
     </parameter>
   </member>
+  <member name="M:TomsToolbox.Core.WeakEventSource`1.Subscribe(System.EventHandler{`0})">
+    <parameter name="handler">
+      <attribute ctor="M:JetBrains.Annotations.NotNullAttribute.#ctor" />
+    </parameter>
+  </member>
+  <member name="M:TomsToolbox.Core.WeakEventSource`1.Unsubscribe(System.EventHandler{`0})">
+    <parameter name="handler">
+      <attribute ctor="M:JetBrains.Annotations.NotNullAttribute.#ctor" />
+    </parameter>
+  </member>
   <member name="M:TomsToolbox.Core.WeakReference`1.#ctor(`0)">
     <parameter name="target">
       <attribute ctor="M:JetBrains.Annotations.CanBeNullAttribute.#ctor" />

TomsToolbox.Core/WeakEventSource.cs

@@ -0,0 +1,152 @@
+namespace TomsToolbox.Core
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Diagnostics.CodeAnalysis;
+    using System.Linq;
+    using System.Reflection;
+
+    using JetBrains.Annotations;
+
+    /// <summary>
+    /// A simple weak event source implementation; useful for static events where you don't want to keep a reference to the event sink.
+    /// </summary>
+    /// <typeparam name="TEventArgs">The type of the event arguments.</typeparam>
+    /// <example>
+    /// Use like this:
+    /// <code language="C#">
+    /// <![CDATA[
+    /// class SampleSource
+    /// {
+    ///     private readonly WeakEventSource<EventArgs> _source = new WeakEventSource<EventArgs>();
+    /// 
+    ///     public event EventHandler AnyAction
+    ///     {
+    ///         add => _sentEventSource.Subscribe(value);
+    ///         remove => _sentEventSource.Unsubscribe(value);
+    ///     }
+    /// 
+    ///     private void OnAnyAction()
+    ///     {
+    ///         _source.Raise(this, EventArgs.Empty);
+    ///     }
+    /// }
+    /// 
+    /// class SampleSink
+    /// {
+    ///     public SampleSink()
+    ///     {
+    ///         var source = new SampleSource();
+    ///         source.AnyAction += Source_AnyAction;
+    ///     }
+    /// 
+    ///     private void Source_AnyAction(object sender, EventArgs e)
+    ///     {
+    ///         ... do something
+    ///     }
+    /// }
+    /// ]]>
+    /// </code>
+    /// </example>
+    public class WeakEventSource<TEventArgs>
+        where TEventArgs : EventArgs
+    {
+        [NotNull, ItemNotNull]
+        // ReSharper disable once AssignNullToNotNullAttribute
+        private readonly List<WeakDelegate> _handlers = new List<WeakDelegate>();
+
+        /// <summary>
+        /// Raises the event with the specified sender and argument.
+        /// </summary>
+        /// <param name="sender">The sender.</param>
+        /// <param name="e">The <see paramref="TEventArgs"/> instance containing the event data.</param>
+        [SuppressMessage("Microsoft.Design", "CA1030:UseEventsWhereAppropriate")]
+        public void Raise(object sender, TEventArgs e)
+        {
+            lock (_handlers)
+            {
+                var garbageCollectedHandlers = _handlers
+                    .Where(h => !h.Invoke(sender, e))
+                    .ToArray();
+
+                _handlers.RemoveRange(garbageCollectedHandlers);
+            }
+        }
+
+        /// <summary>
+        /// Subscribes the specified handler for the event.
+        /// </summary>
+        /// <param name="handler">The handler.</param>
+        public void Subscribe([NotNull] EventHandler<TEventArgs> handler)
+        {
+            // ReSharper disable once AssignNullToNotNullAttribute
+            var weakHandlers = handler
+                .GetInvocationList()
+                // ReSharper disable once AssignNullToNotNullAttribute
+                .Select(d => new WeakDelegate(d))
+                .ToArray();
+
+            lock (_handlers)
+            {
+                _handlers.AddRange(weakHandlers);
+            }
+        }
+
+        /// <summary>
+        /// Unsubscribes the specified handler from the event.
+        /// </summary>
+        /// <param name="handler">The handler.</param>
+        public void Unsubscribe([NotNull] EventHandler<TEventArgs> handler)
+        {
+            lock (_handlers)
+            {
+                while (true)
+                {
+                    var index = _handlers.FindIndex(h1 => h1.Matches(handler));
+                    if (index < 0)
+                        return;
+
+                    _handlers.RemoveAt(index);
+                }
+            }
+
+        }
+
+        private class WeakDelegate
+        {
+            [CanBeNull]
+            private readonly WeakReference _weakTarget;
+            [NotNull]
+            private readonly MethodInfo _method;
+
+            public WeakDelegate([NotNull] Delegate handler)
+            {
+                _weakTarget = handler.Target != null ? new WeakReference(handler.Target) : null;
+                // ReSharper disable once AssignNullToNotNullAttribute
+                _method = handler.GetMethodInfo();
+            }
+
+            public bool Invoke(object sender, TEventArgs e)
+            {
+                object target = null;
+
+                if (_weakTarget != null)
+                {
+                    target = _weakTarget.Target;
+                    if (target == null)
+                        return false;
+                }
+
+                _method.Invoke(target, new[] { sender, e });
+
+                return true;
+            }
+
+            public bool Matches([NotNull] EventHandler<TEventArgs> handler)
+            {
+                return ReferenceEquals(handler.Target, _weakTarget?.Target)
+                       && Equals(handler.GetMethodInfo(), _method);
+            }
+        }
+    }
+}

TomsToolbox.Wpf/Interactivity/MapPanBehavior.cs

@@ -73,6 +73,7 @@ protected override void OnAttached()
             _storyboard.Completed += Storyboard_Completed;
         }
 
+        /// <inheritdoc />
         protected override void OnAssociatedObjectLoaded()
         {
             base.OnAssociatedObjectLoaded();

TomsToolbox.Wpf/Interactivity/MapZoomBehavior.cs

@@ -61,6 +61,7 @@ protected override void OnAttached()
             _storyboard.Completed += Storyboard_Completed;
         }
 
+        /// <inheritdoc />
         protected override void OnAssociatedObjectLoaded()
         {
             base.OnAssociatedObjectLoaded();

TomsToolbox.Wpf/Interactivity/TimerTrigger.cs

@@ -13,7 +13,7 @@
     /// </summary>
     public sealed class TimerTrigger : System.Windows.Interactivity.TriggerBase<FrameworkElement>
     {
-        [CanBeNull] 
+        [CanBeNull]
         private DispatcherTimer _timer;
 
         /// <summary>

TomsToolbox.sln.DotSettings

@@ -3,7 +3,7 @@
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=MemberCanBePrivate_002EGlobal/@EntryIndexedValue">DO_NOT_SHOW</s:String>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=MemberCanBeProtected_002EGlobal/@EntryIndexedValue">DO_NOT_SHOW</s:String>
 	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=UnusedAutoPropertyAccessor_002EGlobal/@EntryIndexedValue">DO_NOT_SHOW</s:String>
-	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=UnusedMember_002EGlobal/@EntryIndexedValue">HINT</s:String>
+	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=UnusedMember_002EGlobal/@EntryIndexedValue">DO_NOT_SHOW</s:String>
 	<s:Int64 x:Key="/Default/CodeStyle/CodeFormatting/CSharpFormat/BLANK_LINES_BETWEEN_USING_GROUPS/@EntryValue">1</s:Int64>
 	<s:String x:Key="/Default/CodeStyle/CodeFormatting/CSharpFormat/PLACE_ACCESSORHOLDER_ATTRIBUTE_ON_SAME_LINE_EX/@EntryValue">NEVER</s:String>
 	<s:Boolean x:Key="/Default/CodeStyle/CSharpUsing/AddImportsToDeepestScope/@EntryValue">True</s:Boolean>