request中的Content_Type

application/json 这个 Content-Type 作为响应头大家肯定不陌生。实际上，现在越来越多的人把它作为请求头，用来告诉服务端(请求行、请求头、实体内容)中实体内容是序列化后的 JSON 字符串。

        /// <summary>
        /// 向服务端请求服务
        /// </summary>
        /// <param name="ServerPage">url字符串</param>
        /// <param name="json"></param>
        /// <returns></returns>
        public static string RegisterImageToServer(string ServerPage, string json)
        {
            //创建请求
            HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(ServerPage);
            request.Method = "POST";
            request.Timeout = 2500;
            request.ContentType = "application/x-www-form-urlencoded; charset=UTF-8";    //告诉服务端(请求行、请求头、实体内容)实体内容的数据类型
            //创建输入流
            //string paraUrlCoded = System.Web.HttpUtility.UrlEncode("paramaters");
            //paraUrlCoded += "=" + System.Web.HttpUtility.UrlEncode(json);
            byte[] payload;
            //将Json字符串转化为字节  
            payload = System.Text.Encoding.UTF8.GetBytes(json);
            //设置请求的ContentLength   
            request.ContentLength = payload.Length;
            //发送请求，获得请求流  
            Stream writer;
            try
            {
                writer = request.GetRequestStream();//获取用于写入请求数据的Stream对象
            }
            catch (Exception)
            {
                writer = null;
                Console.Write("连接服务器失败!");
                return null;
            }
            //将请求参数写入流
            writer.Write(payload, 0, payload.Length);
            writer.Close();//关闭请求流
            //读取返回消息
            string res = string.Empty;
            try
            {
                HttpWebResponse response = (HttpWebResponse)request.GetResponse();
                StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
                res = reader.ReadToEnd();
                reader.Close();
            }
            catch (Exception ex)
            {
                return null;//连接服务器失败
            }
            return res;
        }