private string Post(string num)

        {

            Encoding myEncoding = Encoding.GetEncoding("gb2312");  //选择编码字符集

            string data = "customerSn=6fea75ba52gf339f&phone=" + num + "&cate=fuzhu&channel=hui-5";  //要上传到网页系统里的数据（字段名=数值 ，用&符号连接起来）

            byte[] bytesToPost = System.Text.Encoding.Default.GetBytes(data); //转换为bytes数据

            string responseResult = String.Empty;

            HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create("http://95.163.204.90:2121/api/account/black.json");   //创建一个有效的httprequest请求，地址和端口和指定路径必须要和网页系统工程师确认正确，不然一直通讯不成功

            req.Method = "POST";

            req.ContentType = "application/x-www-form-urlencoded;charset=gb2312";

            req.ContentLength = bytesToPost.Length;

            using (Stream reqStream = req.GetRequestStream())

            {

                reqStream.Write(bytesToPost, 0, bytesToPost.Length);     //把要上传网页系统的数据通过post发送

            }

            HttpWebResponse cnblogsRespone = (HttpWebResponse)req.GetResponse();

            if (cnblogsRespone != null && cnblogsRespone.StatusCode == HttpStatusCode.OK)

            {

                StreamReader sr;

                using (sr = new StreamReader(cnblogsRespone.GetResponseStream()))

                {

                    responseResult = sr.ReadToEnd();  //网页系统的json格式的返回值，在responseResult里，具体内容就是网页系统负责工程师跟你协议号的返回值协议内容

                }

                sr.Close();

            }

            cnblogsRespone.Close();

            return responseResult;

        }