百度地图 获取两点坐标之间的驾车距离（非直线距离） c#

/// <summary>
        /// 根据坐标点获取驾车距离
        /// </summary>
        /// <param name="origins">起点坐标</param>
        /// <param name="destinations">终点坐标</param>
        /// <returns></returns>
        public static string GetDistance(string origins, string destinations)
        {
            try
            {
                //测试数据
                origins = "22.823331,108.326998";
                destinations = "22.832541,108.321788|22.83841,108.294974|22.817868,108.425637|22.883959,108.305368|22.83334,108.32637";

                //行车距离
                string url = "http://api.map.baidu.com/routematrix/v2/driving";
                string ak = "595eRciHjA0MG4TmhTm5ak58M00bQand";
                string param = string.Format("origins={0}&destinations={1}&output=json&ak={2}", origins, destinations, ak);
                string strURL = url + ‘?‘ + param;
                System.Net.HttpWebRequest request;
                request = (System.Net.HttpWebRequest)WebRequest.Create(strURL);
                request.Method = "GET";
                System.Net.HttpWebResponse response;
                response = (System.Net.HttpWebResponse)request.GetResponse();
                System.IO.Stream s;
                s = response.GetResponseStream();
                string StrDate = "";
                string strValue = "";
                StreamReader Reader = new StreamReader(s, Encoding.UTF8);
                while ((StrDate = Reader.ReadLine()) != null)
                {
                    strValue += StrDate + "\r\n";
                }
                return strValue;
            }
            catch (Exception)
            {
            }
            return "";
        }