private void AddConnection(Core.Connectable first, Core.Connectable second)
            {

                mFromShape = first;
                mToShape = second;
                AddConnection();

            }
 public CreateConnectionCommand(Core.Connectable first, Core.Connectable second, Canvas canvas)
 {
     if (canvas == null)
         throw new ArgumentNullException("The canvas cannot be null");
     mFromShape = first;
     mToShape = second;
     mCanvas = canvas;
 }