Code

	  private void OnDiagram_NodeModifying(object sender, NodeValidationEventArgs e)
	  {
		if (e.Node.Bounds.Top < 1 || e.Node.Bounds.Left < 1)
		    e.Cancel = true;
		foreach(DiagramLink link in e.Node.GetAllLinks())
		{
		    if (link.ControlPoints.Count == 3)//Linear link
			  link.Route();
		}
	  }
	  private void OnDiagram_SelectionMoving(object sender, ValidationEventArgs e)
	  {
		Selection selection = m_Diagram.Selection;
		if (selection.Bounds.Top < 1 || selection.Bounds.Left < 1)
		    e.Cancel = true;
	  }