Code

private void OnLinkCreated(object sender, LinkEventArgs e)
{
	DiagramLink l = e.Link;
	DiagramNode o = l.Origin;
	DiagramNode d = l.Destination;

	if (d.IncomingLinks.Count == 1 &&
		Math.Abs(o.Bounds.Y - d.Bounds.Y) < 30)
	 {
		double vcenter = o.Bounds.Y + o.Bounds.Height / 2;
		Rect r = d.Bounds;
		r.Y = vcenter - r.Height / 2;
		d.Bounds = r;

		for (int i = 0; i < l.ControlPoints.Count - 1; ++i)
		{
			Point p = l.ControlPoints[i];
			p.Y = vcenter;
			l.ControlPoints[i] = p;
		}
		l.UpdateFromPoints();
	}
}