Merge pull request #6732 from AvaloniaUI/fixes/6729-itemsrepeater-reassign-items

ItemsRepeater: unsubscribe from ItemsSourceView before disposing it.

src/Avalonia.Controls/Repeater/ItemsRepeater.cs

@@ -588,14 +588,14 @@ namespace Avalonia.Controls
                 throw new AvaloniaInternalException("Cannot set ItemsSourceView during layout.");
             }
 
-            ItemsSourceView?.Dispose();
-            ItemsSourceView = newValue;
-
             if (oldValue != null)
             {
                 oldValue.CollectionChanged -= OnItemsSourceViewChanged;
             }
 
+            ItemsSourceView?.Dispose();
+            ItemsSourceView = newValue;
+
             if (newValue != null)
             {
                 newValue.CollectionChanged += OnItemsSourceViewChanged;

tests/Avalonia.Controls.UnitTests/ItemsRepeaterTests.cs

@@ -0,0 +1,24 @@
+using System.Collections.ObjectModel;
+using Xunit;
+
+namespace Avalonia.Controls.UnitTests
+{
+    public class ItemsRepeaterTests
+    {
+        [Fact]
+        public void Can_Reassign_Items()
+        {
+            var target = new ItemsRepeater();
+            target.Items = new ObservableCollection<string>();
+            target.Items = new ObservableCollection<string>();
+        }
+
+        [Fact]
+        public void Can_Reassign_Items_To_Null()
+        {
+            var target = new ItemsRepeater();
+            target.Items = new ObservableCollection<string>();
+            target.Items = null;
+        }
+    }
+}