WIP

src/Avalonia.Controls/Primitives/SelectingItemsControl.cs

@@ -876,7 +876,7 @@ namespace Avalonia.Controls.Primitives
 
         private void OnItemsViewSourceChanged(object? sender, EventArgs e)
         {
-            if (_selection is not null)
+            if (_selection is not null && _updateState is null)
                 _selection.Source = ItemsView.Source;
         }
 

src/Avalonia.Controls/Selection/InternalSelectionModel.cs

@@ -21,8 +21,6 @@ namespace Avalonia.Controls.Selection
             SourceReset += OnSourceReset;
         }
 
-        public bool DataContextIsUpdating { get; set; }
-
         [AllowNull]
         public IList WritableSelectedItems
         {

src/Avalonia.Controls/VirtualizingPanel.cs

@@ -193,13 +193,13 @@ namespace Avalonia.Controls
                 throw new InvalidOperationException("The VirtualizingPanel is already attached to an ItemsControl");
 
             ItemsControl = itemsControl;
-            ItemsControl.ItemsView.CollectionChanged += OnItemsControlItemsChanged;
+            ItemsControl.ItemsView.PostCollectionChanged += OnItemsControlItemsChanged;
         }
 
         internal void Detach()
         {
             var itemsControl = EnsureItemsControl();
-            itemsControl.ItemsView.CollectionChanged -= OnItemsControlItemsChanged;
+            itemsControl.ItemsView.PostCollectionChanged -= OnItemsControlItemsChanged;
             ItemsControl = null;
             Children.Clear();
         }