WAF Add WeakEvent.TryRemove method

src/System.Waf/Samples/InformationManager/AddressBook.Modules.Applications/Controllers/SelectContactController.cs

@@ -12,7 +12,7 @@ internal class SelectContactController
     private readonly SelectContactViewModel selectContactViewModel;
     private readonly DelegateCommand selectContactCommand;
     private ObservableListView<Contact> contactsView = null!;
-    private IWeakEventProxy contactListViewModelPropertyChangedProxy = null!;
+    private IWeakEventProxy? contactListViewModelPropertyChangedProxy;
 
     [ImportingConstructor]
     public SelectContactController(SelectContactViewModel selectContactViewModel, ContactListViewModel contactListViewModel)
@@ -44,7 +44,7 @@ public void Initialize()
 
     public void Shutdown()
     {
-        contactListViewModelPropertyChangedProxy.Remove();
+        WeakEvent.TryRemove(ref contactListViewModelPropertyChangedProxy);
         contactsView.Dispose();
     }
 

src/System.Waf/Samples/InformationManager/EmailClient.Modules.Applications/Controllers/EmailFolderController.cs

@@ -50,7 +50,7 @@ public void Initialize()
 
     public void Shutdown()
     {
-        emailListViewModelPropertyChangedProxy?.Remove();
+        WeakEvent.TryRemove(ref emailListViewModelPropertyChangedProxy);
         // Set the views to null so that the garbage collector can collect them.
         emailLayoutViewModel.EmailListView = null;
         emailLayoutViewModel.EmailView = null;

src/System.Waf/Samples/InformationManager/EmailClient.Modules.Applications/ViewModels/NewEmailViewModel.cs

@@ -43,7 +43,7 @@ public Email Email
         set
         {
             if (email == value) return;
-            emailPropertyChangedProxy?.Remove();
+            WeakEvent.TryRemove(ref emailPropertyChangedProxy);
             email = value;
             emailPropertyChangedProxy = WeakEvent.PropertyChanged.Add(email, EmailPropertyChanged);
             UpdateProperties();

src/System.Waf/System.Waf/System.Waf.Core.Test/Foundation/WeakEventStaticEventHandlerTest.cs

@@ -80,6 +80,25 @@ public void WeakEventAddArgumentException()
             AssertHelper.ExpectedException<ArgumentNullException>(() => WeakEvent.StaticEventHandler.Add(subscriber.Handler, h => StaticPublisher.Event1 += h, null!));
         }
 
+        [TestMethod]
+        public void WeakEventRemoveTest()
+        {
+            var subscriber = new Subscriber();
+            var proxy = WeakEvent.StaticEventHandler.Add(subscriber.Handler, h => StaticPublisher.Event1 += h, h => StaticPublisher.Event1 -= h);
+            StaticPublisher.RaiseEvent();
+            Assert.AreEqual(1, subscriber.HandlerCallCount);
+
+            WeakEvent.TryRemove(ref proxy);
+            StaticPublisher.RaiseEvent();
+            Assert.AreEqual(1, subscriber.HandlerCallCount);
+            Assert.IsNull(proxy);
+
+            WeakEvent.TryRemove(ref proxy);
+            StaticPublisher.RaiseEvent();
+            Assert.AreEqual(1, subscriber.HandlerCallCount);
+            Assert.IsNull(proxy);
+        }
+
         private static (WeakReference<Manager>, WeakReference<Subscriber>) WeakEventHandlerCore(Manager? manager, Subscriber? subscriber,
             int raiseCount = 1, int addCount = 1, bool remove = false, bool removeTwice = false)
         {

src/System.Waf/System.Waf/System.Waf.Core/Foundation/WeakEvent.cs

@@ -370,5 +370,13 @@ public static IWeakEventProxy Add(INotifyDataErrorInfo source, S.EventHandler<Da
                 return EventHandler<DataErrorsChangedEventArgs>.Add(source, targetHandler, (s, h) => s.ErrorsChanged += h, (s, h) => s.ErrorsChanged -= h);
             }
         }
+
+        /// <summary>Remove the weak event handler if the passed proxy is not null. And set the proxy to null.</summary>
+        /// <param name="proxy">The weak event proxy.</param>
+        public static void TryRemove(ref IWeakEventProxy? proxy)
+        {
+            proxy?.Remove();
+            proxy = null;
+        }
     }
 }

src/System.Waf/System.Waf/System.Waf.Wpf/Applications/ObservableListView.cs

@@ -17,7 +17,7 @@ namespace System.Waf.Applications
     /// <typeparam name="T">The type of elements in the collection.</typeparam>
     public class ObservableListView<T> : ObservableListViewCore<T>
     {
-        private readonly IWeakEventProxy? originalCollectionChangedProxy;
+        private IWeakEventProxy? originalCollectionChangedProxy;
 
         /// <summary>Initializes a new instance of the ObservableListView class that represents a view of the specified list.</summary>
         /// <param name="originalList">The original list.</param>
@@ -55,7 +55,7 @@ protected override void OnDispose(bool disposing)
         {
             if (disposing)
             {
-                originalCollectionChangedProxy?.Remove();
+                WeakEvent.TryRemove(ref originalCollectionChangedProxy);
             }
             base.OnDispose(disposing);
         }

src/System.Waf/System.Waf/System.Waf.Wpf/Applications/SynchronizingCollection.cs

@@ -18,7 +18,7 @@ namespace System.Waf.Applications
     [Obsolete("Use System.Waf.Foundation.SynchronizingList instead.")]
     public class SynchronizingCollection<T, TOriginal> : SynchronizingCollectionCore<T, TOriginal>
     {
-        private readonly IWeakEventProxy? originalCollectionChangedProxy;
+        private IWeakEventProxy? originalCollectionChangedProxy;
 
         /// <summary>Initializes a new instance of the <see cref="SynchronizingCollection{T, TOriginal}"/> class.</summary>
         /// <param name="originalCollection">The original collection.</param>
@@ -40,7 +40,7 @@ protected override void OnDispose(bool disposing)
         {
             if (disposing)
             {
-                originalCollectionChangedProxy?.Remove();
+                WeakEvent.TryRemove(ref originalCollectionChangedProxy);
             }
             base.OnDispose(disposing);
         }