Code

diagram.LinkCrossings = LinkCrossings.Cut;
diagram.ValidateLinkCrossing += OnValidateLinkCrossing;

void OnValidateLinkCrossing(object sender, LinkCrossingEventArgs e)
{
	if (e.BottomLink.StrokeDashStyle != DashStyles.Solid)
		e.Cancel = true;
} 

Code

public DiagramLink TopLink { get; set; }
public int TopSegmentIndex { get; set; }

public DiagramLink BottomLink { get; set; }
public int BottomSegmentIndex { get; set; }

public Point IntersectionPoint { get; set; }

public bool Cancel { get; set; }