Use weak event handlers.

Seems that C++/WinRT uses weak event handlers by default so we need to do the same here.

src/Avalonia.Controls/Repeater/ItemsRepeater.cs

@@ -7,10 +7,10 @@ using System;
 using System.Collections;
 using System.Collections.Specialized;
 using Avalonia.Controls.Templates;
-using Avalonia.Data;
 using Avalonia.Input;
 using Avalonia.Layout;
 using Avalonia.Logging;
+using Avalonia.Utilities;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Controls
@@ -681,8 +681,15 @@ namespace Avalonia.Controls
             if (oldValue != null)
             {
                 oldValue.UninitializeForContext(LayoutContext);
-                oldValue.MeasureInvalidated -= InvalidateMeasureForLayout;
-                oldValue.ArrangeInvalidated -= InvalidateArrangeForLayout;
+
+                WeakEventHandlerManager.Unsubscribe<EventArgs, ItemsRepeater>(
+                    oldValue,
+                    nameof(newValue.MeasureInvalidated),
+                    InvalidateMeasureForLayout);
+                WeakEventHandlerManager.Unsubscribe<EventArgs, ItemsRepeater>(
+                    oldValue,
+                    nameof(newValue.ArrangeInvalidated),
+                    InvalidateArrangeForLayout);
 
                 // Walk through all the elements and make sure they are cleared
                 foreach (var element in Children)
@@ -699,8 +706,15 @@ namespace Avalonia.Controls
             if (newValue != null)
             {
                 newValue.InitializeForContext(LayoutContext);
-                newValue.MeasureInvalidated += InvalidateMeasureForLayout;
-                newValue.ArrangeInvalidated += InvalidateArrangeForLayout;
+
+                WeakEventHandlerManager.Subscribe<AttachedLayout, EventArgs, ItemsRepeater>(
+                    newValue,
+                    nameof(newValue.MeasureInvalidated),
+                    InvalidateMeasureForLayout);
+                WeakEventHandlerManager.Subscribe<AttachedLayout, EventArgs, ItemsRepeater>(
+                    newValue,
+                    nameof(newValue.ArrangeInvalidated),
+                    InvalidateArrangeForLayout);
             }
 
             bool isVirtualizingLayout = newValue != null && newValue is VirtualizingLayout;