Handle move and replace in virtualized lists.

src/Avalonia.Controls/Presenters/ItemVirtualizerSimple.cs

@@ -104,6 +104,11 @@ namespace Avalonia.Controls.Presenters
 
                         break;
 
+                    case NotifyCollectionChangedAction.Move:
+                    case NotifyCollectionChangedAction.Replace:
+                        RecycleContainers();
+                        break;
+
                     case NotifyCollectionChangedAction.Reset:
                         RecycleContainersOnRemove();
                         break;

tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs

@@ -303,6 +303,51 @@ namespace Avalonia.Controls.UnitTests.Presenters
             Assert.Equal(expected, actual);
         }
 
+        [Fact]
+        public void Replacing_Items_Should_Update_Containers()
+        {
+            var target = CreateTarget(itemCount: 20);
+
+            target.ApplyTemplate();
+            target.Measure(new Size(100, 100));
+            target.Arrange(new Rect(0, 0, 100, 100));
+
+            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+            var items = (ObservableCollection<string>)target.Items;
+            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+
+            Assert.Equal(expected, actual);
+
+            items[4] = expected[4] = "Replaced";
+
+            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+            Assert.Equal(expected, actual);
+        }
+
+        [Fact]
+        public void Moving_Items_Should_Update_Containers()
+        {
+            var target = CreateTarget(itemCount: 20);
+
+            target.ApplyTemplate();
+            target.Measure(new Size(100, 100));
+            target.Arrange(new Rect(0, 0, 100, 100));
+
+            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+            var items = (ObservableCollection<string>)target.Items;
+            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+
+            Assert.Equal(expected, actual);
+
+            items.Move(4, 8);
+            var i = expected[4];
+            expected.RemoveAt(4);
+            expected.Insert(8, i);
+
+            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+            Assert.Equal(expected, actual);
+        }
+
         [Fact]
         public void Setting_Items_To_Null_Should_Remove_Containers()
         {