Code

private DiagramLink newLink = null;

private void diagramView_DragDrop(object sender, DragEventArgs e)
{
	PointF point = diagramView.ClientToDoc(
		diagramView.PointToClient(new Point(e.X, e.Y)));
	DiagramNode node = diagram.GetNodeAt(point);
	if (node != null)
	{
		e.Effect = DragDropEffects.Copy;

		newLink = diagram.Factory.CreateDiagramLink(node, point);
	}
}

private void diagramView_MouseMove(object sender, MouseEventArgs e)
{
	if (newLink != null)
	{
		diagram.Invalidate(newLink.GetRepaintRect(false));
		PointF point = diagramView.ClientToDoc(e.Location);

		PointCollection cp = newLink.ControlPoints;
		cp[cp.Count - 1] = point;
		newLink.UpdateFromPoints();
	}
}

private void diagramView_MouseUp(object sender, MouseEventArgs e)
{
	if (newLink != null)
	{
		PointF point = diagramView.ClientToDoc(e.Location);
		DiagramNode node = diagram.GetNodeAt(point);
		if (node != null)
			newLink.Destination = node;
		newLink.UpdateIntersections();
		newLink = null;
	}
}