private void Layout_ElementRemoved(object sender, LayoutElementEventArgs e)
        {
            if (_suspendLayoutItemCreation)
                return;

            CollectLayoutItemsDeleted();
        }
        private void Layout_ElementAdded(object sender, LayoutElementEventArgs e)
        {
            if (_suspendLayoutItemCreation)
                return;

            foreach (var content in Layout.Descendents().OfType<LayoutContent>())
            {
                if (content is LayoutDocument)
                    CreateDocumentLayoutItem(content as LayoutDocument);
                else //if (content is LayoutAnchorable)
                    CreateAnchorableLayoutItem(content as LayoutAnchorable);
            }

            CollectLayoutItemsDeleted();
        }