private void NotifyItemUpdatedWorker(NotificationArgs args)
        {
            ItemPropertyChanged(args);

            if (IsRealItem(ParentItem))
            {
                NotificationArgs parentArgs = args;
                parentArgs.ChangeSource = HierarchicalChangeSource.ChildItem;
                ParentItem.NotifyItemUpdatedWorker(parentArgs);
            }

            if (IsRealItem(OwnerItem))
            {
                NotificationArgs ownerArgs = args;
                ownerArgs.ChangeSource = HierarchicalChangeSource.OwnedItem;
                OwnerItem.NotifyItemUpdatedWorker(ownerArgs);
            }
        }