protected override void OnItemsChanged(IList <T> oldValue, IList <T> newValue) { base.OnItemsChanged(oldValue, newValue); AddCommand.InvalidateCanExecute(); RemoveCommand.InvalidateCanExecute(); CloneCommand.InvalidateCanExecute(); MoveUpCommand.InvalidateCanExecute(); MoveDownCommand.InvalidateCanExecute(); ClearCommand.InvalidateCanExecute(); ExportCommand.InvalidateCanExecute(); }