public void AddLayoutListDraggable(UIElement element)
 {
     RemoveLayoutListDraggable(element);
     layoutListDragEventSource.Attach(element);
 }
 public void AddAvailableListDraggable(UIElement element)
 {
     RemoveAvailableListDraggable(element);
     availableListDragEventSource.Attach(element);
 }