Code

private void UntangleLink(DiagramLink NewLink)
{
    try
    {
        if (NewLink.Origin == NewLink.Destination)
        {
            //it's self referential
            NewLink.Style = LinkStyle.Polyline;
            NewLink.Route();
            return;
        }
        //get all common links between start and end state
        DiagramLinkCollection commonLinks = GetCommonLinks(NewLink.Origin, NewLink.Destination);
        if (commonLinks.Count > 1)
        {
            //get the start and end point of the calling link
            Point pt1 = NewLink.ControlPoints[0];
            Point pt2 = NewLink.ControlPoints[NewLink.ControlPoints.Count - 1];
            //loop thru all the common links
            for (int c = 0; c < commonLinks.Count; ++c)
            {
                DiagramLink link = commonLinks[c];
                link.Style = LinkStyle.Bezier;
                //reset to one segment
                link.SegmentCount = 1;
                //get new control points
                Point cp1 = new Point(pt1.X + 1 * (pt2.X - pt1.X) / 3, pt1.Y + 1 * (pt2.Y - pt1.Y) / 3);
                Point cp2 = new Point(pt1.X + 2 * (pt2.X - pt1.X) / 3, pt1.Y + 2 * (pt2.Y - pt1.Y) / 3);
                float angle = 0, radius = 0;
                CartesianToPolar(pt1, pt2, ref angle, ref radius);
                int pairOffset = (c / 2 + 1) * 10;
                //if (commonLinks.Count % 2 == 0)
                //{
                PolarToCartesian(cp1, c % 2 == 0 ? angle - 90 : angle + 90, pairOffset, ref cp1);
                PolarToCartesian(cp2, c % 2 == 0 ? angle - 90 : angle + 90, pairOffset, ref cp2);
                if (link.ControlPoints[0] == pt1)
                {
                    link.ControlPoints[1] = cp1;
                    link.ControlPoints[2] = cp2;
                }
                else
                {
                    link.ControlPoints[1] = cp2;
                    link.ControlPoints[2] = cp1;
                }
                link.UpdateFromPoints();
                //}
            }
        }
    }
    catch (Exception exc)
    {
        AUISL.Utilities.LogException(exc);
    }
}

DiagramLinkCollection GetCommonLinks(DiagramNode node1, DiagramNode node2)
{
    DiagramLinkCollection commonLinks = new DiagramLinkCollection();
    foreach (DiagramLink link in node1.OutgoingLinks)
    if (link.Destination == node2)
        commonLinks.Add(link);
    foreach (DiagramLink link in node1.IncomingLinks)
        if (link.Origin == node2)
            commonLinks.Add(link);
    return commonLinks;
}

void PolarToCartesian(Point coordCenter, float a, float r, ref Point cartesian)
{
    if (r == 0)
    {
        cartesian = coordCenter;
        return;
    }
    cartesian.X = (float)(coordCenter.X + Math.Cos(a * Math.PI / 180) * r);
    cartesian.Y = (float)(coordCenter.Y - Math.Sin(a * Math.PI / 180) * r);
}

void CartesianToPolar(Point coordCenter, Point cartesian, ref float a, ref float r)
{
    if (coordCenter == cartesian)
    {
        a = 0;
        r = 0;
        return;
    }
    double dx = cartesian.X - coordCenter.X;
    double dy = cartesian.Y - coordCenter.Y;
    r = (float)(Math.Sqrt(Math.Pow(dx, 2) + Math.Pow(dy, 2)));
    a = (float)(Math.Atan(-dy / dx) * 180 / Math.PI);
    if (dx < 0) a += 180;
}