Code

private void insertBezierSegment(Arrow arrow, int segment)
{
	if (arrow.Style != ArrowStyle.Bezier)
		throw new ArgumentException("not a Bezier");

	if (segment > arrow.SegmentCount)
		throw new ArgumentException("invalid segment index");

	PointCollection savedPoints = arrow.ControlPoints.Clone();

	// this resets the coordinates of all existing points
	arrow.SegmentCount++;

	// restore the points of the old segments
	for (int i = 0; i < segment * 4; ++i)
		arrow.ControlPoints[i] = savedPoints[i];
	for (int i = (segment + 1) * 4; i < arrow.ControlPoints.Count; ++i)
		arrow.ControlPoints[i] = savedPoints[i - 3];
}