public static List <Point> GetIntersectionPoints(List <Line> lines1, List <Line> lines2)
 {
     return((from line1 in lines1
             from line2 in lines2
             where line1.Intersects(line2)
             select LineHelper.CalculateIntersectionPoint(line1, line2)
             into intersectionPoint
             where intersectionPoint.X != 0 || intersectionPoint.Y != 0
             select intersectionPoint).ToList());
 }