Selector doesn't change selection properties when disconnected

src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Controls/Primitives/Selector.cs

@@ -1110,6 +1110,16 @@ internal virtual void UnselectAllImpl()
         /// <param name="e">Information about what has changed</param>
         protected override void OnItemsChanged(NotifyCollectionChangedEventArgs e)
         {
+            base.OnItemsChanged(e);
+
+            // if the selector is disconnected, don't do any more work - it
+            // wouldn't help, and could actually hurt, e.g. by sending bad
+            // values through bindings attached to the selection properties.
+            if (DataContext == BindingExpressionBase.DisconnectedItem)
+            {
+                return;
+            }
+
             // When items become available, reevaluate the choice of algorithm
             // used by _selectedItems.
             if (e.Action == NotifyCollectionChangedAction.Reset ||
@@ -1119,8 +1129,6 @@ protected override void OnItemsChanged(NotifyCollectionChangedEventArgs e)
                 ResetSelectedItemsAlgorithm();
             }
 
-            base.OnItemsChanged(e);
-
             // Do not coerce the SelectedIndexProperty if it holds a DeferredSelectedIndexReference
             // because this deferred reference object is guaranteed to produce a pre-coerced value.
             // Also if you did coerce it then you will lose the attempted performance optimization