protected override void OnAfterLabelEdit(NodeLabelEditEventArgs e)
 {
     if (string.IsNullOrEmpty(e.Label))
     {
         e.CancelEdit = true;
         return;
     }
     if (e.Node is AlbumNode)
     {
         AlbumNode node = e.Node as AlbumNode;
         e.CancelEdit = !node.RenameAlbum(e.Label);
     }
     else if (e.Node is PhotoNode)
     {
         PhotoNode node = e.Node as PhotoNode;
         node.Photograph.Caption = e.Label;
         SaveAlbumChanges();
     }
 }