C#+AE 二次开发 T型

对于T字形相交，返回想要的点集，判断出交点

        private List xjdIntersection(IPointCollection fnPointCollection, IPointCollection foPointCollection)
        {
            List pointList = new List();//相交的线的的点集
            LineIntersection lis = new LineIntersection();
            IPoint xjPoint = (IPoint)new PointClass();
            Point pointA = new Point();
            Point pointB = new Point();
            Point pointC = new Point();
            Point pointD = new Point();

            bool res = false;
            for (int i = 0; i < fnPointCollection.PointCount - 1; i++)
            {
                for (int j = i + 1; j < i + 2; j++)
                {
                    pointA = (Point)fnPointCollection.get_Point(i);
                    pointB = (Point)fnPointCollection.get_Point(j);
                    int m = 0;
                    for (; m < foPointCollection.PointCount - 1; m++)
                    {
                        for (int n = m + 1; n < m + 2; n++)
                        {
                            pointC = (Point)foPointCollection.get_Point(m);
                            pointD = (Point)foPointCollection.get_Point(n);

                            res = lis.pdIntersection(pointA, pointB, pointC, pointD, ref xjPoint);
                            if (res == true)
                            {
                                pointList.Add(pointA);
                                pointList.Add(pointB);
                                pointList.Add(pointC);
                                pointList.Add(pointD);
                            }
                        }
                    }
                }
            }
            return pointList;
        }