Add IsSelectedChanged property

src/Avalonia.Controls/Primitives/SelectingItemsControl.cs

@@ -103,7 +103,7 @@ namespace Avalonia.Controls.Primitives
         /// </summary>
         public static readonly RoutedEvent<RoutedEventArgs> IsSelectedChangedEvent =
             RoutedEvent.Register<SelectingItemsControl, RoutedEventArgs>(
-                "IsSelectedChanged",
+                nameof(IsSelectedChanged),
                 RoutingStrategies.Bubble);
 
         /// <summary>
@@ -139,6 +139,17 @@ namespace Avalonia.Controls.Primitives
             IsSelectedChangedEvent.AddClassHandler<SelectingItemsControl>((x, e) => x.ContainerSelectionChanged(e));
         }
 
+        /// <summary>
+        /// Event that should be raised by items that implement <see cref="ISelectable"/> to
+        /// notify the parent <see cref="SelectingItemsControl"/> that their selection state
+        /// has changed.
+        /// </summary>
+        public event EventHandler<RoutedEventArgs>? IsSelectedChanged
+        {
+            add { AddHandler(IsSelectedChangedEvent, value); }
+            remove { RemoveHandler(IsSelectedChangedEvent, value); }
+        }
+
         /// <summary>
         /// Occurs when the control's selection changes.
         /// </summary>