Code

	  /// <summary>
	  /// Occurs when mouse pointer is over the link and left button is down
	  /// </summary>
	  /// <param name="sender">Sender object</param>
	  /// <param name="e">Provides arguments for this event</param>
	  private void OnLinkMouseLeftButtonDown(object sender, MouseEventArgs e)
	  {
		DiagramLink link = sender as DiagramLink;
		Point mousePos = e.MouseDevice.GetPosition(m_Diagram);
		//foreach(Point ctrlPnt in link.ControlPoints)
		for (int i = 0; i < link.ControlPoints.Count; ++i)
		{
		    Point ctrlPnt = link.ControlPoints[i];
		    if (Math.Abs(mousePos.X - ctrlPnt.X) < 0.5)
		    {
			  Point nextCtrlPnt = link.ControlPoints[i + 1];
			  Point newPnt = new Point();
			  newPnt.X = ctrlPnt.X;
			  Point nextNewPnt = new Point();
			  nextNewPnt.X = ctrlPnt.X;
			  if (ctrlPnt.Y < nextCtrlPnt.Y)
			  {
				newPnt.Y = ctrlPnt.Y + 15;
				nextNewPnt.Y = nextCtrlPnt.Y - 15;
				link.ControlPoints.Insert(i + 1, newPnt);
				link.ControlPoints.Insert(i + 2, nextNewPnt);
			  }
			  else
			  {
				newPnt.Y = ctrlPnt.Y - 15;
				nextNewPnt.Y = nextCtrlPnt.Y + 15;
				link.ControlPoints.Insert(i + 2, newPnt);
				link.ControlPoints.Insert(i + 1, nextNewPnt);
			  }
			  link.UpdateFromPoints(false, false);
			  break;
		    }
		    else if (Math.Abs(mousePos.Y - ctrlPnt.Y) < 0.5)
		    {
			  //To do: Add horisontal segment
		    }
		}
	  } 

Code

m_Diagram.Behavior = Behavior.DrawLinks;
 

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m_Diagram.Behavior = Behavior.Custom;
m_Diagram.CustomBehavior = new LinkBehavior(m_Diagram);
 

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return base.StartDraw(point);
 

Code

            var node = Diagram.GetNodeAt(point);
            if (node == null)
                return new InteractionState(Diagram.Selection, 0, Action.Create);
            return base.StartDraw(point);