Automatically dispatch PropertyChanged notification to the UI thread

src/Avalonia.Base/Data/Core/IndexerNodeBase.cs

@@ -22,7 +22,7 @@ namespace Avalonia.Data.Core
 
             if (target is INotifyPropertyChanged inpc)
             {
-                WeakEvents.PropertyChanged.Subscribe(inpc, this);
+                WeakEvents.ThreadSafePropertyChanged.Subscribe(inpc, this);
             }
             
             ValueChanged(GetValue(target));
@@ -39,7 +39,7 @@ namespace Avalonia.Data.Core
 
                 if (target is INotifyPropertyChanged inpc)
                 {
-                    WeakEvents.PropertyChanged.Unsubscribe(inpc, this);
+                    WeakEvents.ThreadSafePropertyChanged.Unsubscribe(inpc, this);
                 }
             }
         }

src/Avalonia.Base/Data/Core/Plugins/InpcPropertyAccessorPlugin.cs

@@ -160,7 +160,7 @@ namespace Avalonia.Data.Core.Plugins
                 var inpc = GetReferenceTarget() as INotifyPropertyChanged;
 
                 if (inpc != null) 
-                    WeakEvents.PropertyChanged.Unsubscribe(inpc, this);
+                    WeakEvents.ThreadSafePropertyChanged.Unsubscribe(inpc, this);
             }
 
             private object? GetReferenceTarget()
@@ -185,7 +185,7 @@ namespace Avalonia.Data.Core.Plugins
                 var inpc = GetReferenceTarget() as INotifyPropertyChanged;
 
                 if (inpc != null) 
-                    WeakEvents.PropertyChanged.Subscribe(inpc, this);
+                    WeakEvents.ThreadSafePropertyChanged.Subscribe(inpc, this);
             }
         }
     }

src/Avalonia.Base/Utilities/WeakEvents.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Specialized;
 using System.ComponentModel;
 using System.Windows.Input;
+using Avalonia.Threading;
 
 namespace Avalonia.Utilities;
 
@@ -20,15 +21,30 @@ public class WeakEvents
             });
     
     /// <summary>
-    /// Represents PropertyChanged event from <see cref="INotifyPropertyChanged"/>
+    /// Represents PropertyChanged event from <see cref="INotifyPropertyChanged"/> with auto-dispatching to the UI thread
     /// </summary>
     public static readonly WeakEvent<INotifyPropertyChanged, PropertyChangedEventArgs>
-        PropertyChanged = WeakEvent.Register<INotifyPropertyChanged, PropertyChangedEventArgs>(
+        ThreadSafePropertyChanged = WeakEvent.Register<INotifyPropertyChanged, PropertyChangedEventArgs>(
             (s, h) =>
             {
-                PropertyChangedEventHandler handler = (_, e) => h(s, e);
+                bool unsubscribed = false;
+                PropertyChangedEventHandler handler = (_, e) =>
+                {
+                    if (Dispatcher.UIThread.CheckAccess())
+                        h(s, e);
+                    else
+                        Dispatcher.UIThread.Post(() =>
+                        {
+                            if (!unsubscribed)
+                                h(s, e);
+                        });
+                };
                 s.PropertyChanged += handler;
-                return () => s.PropertyChanged -= handler;
+                return () =>
+                {
+                    unsubscribed = true;
+                    s.PropertyChanged -= handler;
+                };
             });
 
 

src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/PropertyInfoAccessorFactory.cs

@@ -121,7 +121,7 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
         {
             if (_reference.TryGetTarget(out var o) && o is INotifyPropertyChanged inpc)
             {
-                WeakEvents.PropertyChanged.Unsubscribe(inpc, this);
+                WeakEvents.ThreadSafePropertyChanged.Unsubscribe(inpc, this);
             }
         }
 
@@ -138,7 +138,7 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
         private void SubscribeToChanges()
         {
             if (_reference.TryGetTarget(out var o) && o is INotifyPropertyChanged inpc)
-                WeakEvents.PropertyChanged.Subscribe(inpc, this);
+                WeakEvents.ThreadSafePropertyChanged.Subscribe(inpc, this);
         }
     }