(#149) Updated xUnit, fixed .NET 9 synchronization context bug from .NET 9 performance improvements.

Author: Adrian Hall

Directory.Packages.props

@@ -33,7 +33,7 @@
     <PackageVersion Include="System.Text.Json" Version="8.0.5" />
     <PackageVersion Include="System.Text.RegularExpressions" Version="4.3.1" />
     <PackageVersion Include="System.Threading.Tasks.Dataflow" Version="8.0.1" />
-    <PackageVersion Include="xunit" Version="2.7.0" />
+    <PackageVersion Include="xunit" Version="2.9.2" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="2.5.7" />
     <PackageVersion Include="coverlet.collector" Version="6.0.2" />
     <PackageVersion Include="coverlet.msbuild" Version="6.0.2" />

src/CommunityToolkit.Datasync.Client/Paging/ConcurrentObservableCollection.cs

@@ -16,7 +16,7 @@ namespace CommunityToolkit.Datasync.Client;
 /// <typeparam name="T"></typeparam>
 public class ConcurrentObservableCollection<T> : ObservableCollection<T>
 {
-    private readonly SynchronizationContext context = SynchronizationContext.Current!;
+    private readonly SynchronizationContext? currentContext = SynchronizationContext.Current;
     private bool suppressNotification = false;
 
     /// <summary>
@@ -151,31 +151,30 @@ public bool ReplaceIf(Func<T, bool> match, T replacement)
     /// </summary>
     /// <param name="e">The event arguments</param>
     protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
-        => DispatchCallback(new SynchronizationContextAdapter(this.context), RaiseCollectionChanged, e);
+    {
+        if (this.currentContext is null || SynchronizationContext.Current == this.currentContext)
+        {
+            RaiseCollectionChanged(e);
+        }
+        else
+        {
+            this.currentContext.Send(RaiseCollectionChanged, e);
+        }
+    }
 
     /// <summary>
     /// Event trigger to indicate that a property has changed in a thread-safe way.
     /// </summary>
     /// <param name="e">The event arguments</param>
     protected override void OnPropertyChanged(PropertyChangedEventArgs e)
-        => DispatchCallback(new SynchronizationContextAdapter(this.context), RaisePropertyChanged, e);
-
-    /// <summary>
-    /// Dispatches the callback to the synchronization context.  If the synchronization context is
-    /// the current one, we can avoid a dispatch and just call the callback directly.
-    /// </summary>
-    /// <param name="context">The context to send the request to.</param>
-    /// <param name="callback">The callback method.</param>
-    /// <param name="param">The parameter for the callback method.</param>
-    internal static void DispatchCallback(ISynchronizationContext context, SendOrPostCallback callback, object? param)
     {
-        if (context.IsCurrentContext())
+        if (this.currentContext is null || SynchronizationContext.Current == this.currentContext)
         {
-            callback(param);
+            RaisePropertyChanged(e);
         }
         else
         {
-            context.Send(callback, param);
+            this.currentContext.Send(RaisePropertyChanged, e);
         }
     }
 

src/CommunityToolkit.Datasync.Client/Paging/SynchronizationContextAdapter.cs

@@ -180,40 +180,4 @@ public void ReplaceIf_False_IfNoMatch()
         actual.Should().BeFalse();
         this.movies.Should().HaveCount(count).And.NotContain(item);
     }
-
-    [Fact]
-    public void DispatchCallback_DispatchesToSynchronizationContext()
-    {
-        int contextCaller = 0;
-        int functionCaller = 0;
-
-        void dispatcher(object p) { functionCaller++; }
-
-        ISynchronizationContext context = Substitute.For<ISynchronizationContext>();
-        context.IsCurrentContext().Returns(false);
-        context.When(x => x.Send(Arg.Any<SendOrPostCallback>(), Arg.Any<object>())).Do(x => contextCaller++);
-
-        ConcurrentObservableCollection<InMemoryMovie>.DispatchCallback(context, dispatcher, new object());
-
-        contextCaller.Should().Be(1);
-        functionCaller.Should().Be(0);
-    }
-
-    [Fact]
-    public void DispatchCallback_DispatchesLocally()
-    {
-        int contextCaller = 0;
-        int functionCaller = 0;
-
-        void dispatcher(object p) { functionCaller++; }
-
-        ISynchronizationContext context = Substitute.For<ISynchronizationContext>();
-        context.IsCurrentContext().Returns(true);
-        context.When(x => x.Send(Arg.Any<SendOrPostCallback>(), Arg.Any<object>())).Do(x => contextCaller++);
-
-        ConcurrentObservableCollection<InMemoryMovie>.DispatchCallback(context, dispatcher, new object());
-
-        contextCaller.Should().Be(0);
-        functionCaller.Should().Be(1);
-    }
 }