C# NTS 获取MuliiLineString中的所有线

/// 

        /// 获取多段线的所有线
        /// 
        /// 
        /// 
        public static List GetLineStrings(this MultiLineString ml)
        {
            List lineStrings = new List();

            for (int i=0;i< ml.NumGeometries;i++)
            {
                var m = ml.GetGeometryN(i);

                if (m is LineString)
                {
                    lineStrings.Add(m as LineString);
                }
                else if (m is MultiLineString)
                {
                    var mm = (MultiLineString)m;
                    lineStrings.AddRange(mm.GetLineStrings());
                }
            }


            return lineStrings;
        }