/// <summary>
/// Crawls the VisualTree of the given UIElement and registers all
/// elements participating in the DragDrop framework.
/// </summary>
/// <param name="startingWith"></param>
public void RegisterAllDragDropParticipants(UIElement startingWith)
{
startingWith
.FindAllElementsByType<IDragDropSource>()
.Where(o => !_sources.Contains(o))
.Subscribe(RegisterDragDropSource);
startingWith
.FindAllElementsByType<IDragDropTarget>()
.Where(o => !_targets.Contains(o))
.Subscribe(RegisterDragDropTarget);
}
