C#Post提交

          var dic = new SortedDictionarystring, string>
            {
                {"name", "test"},
                {"pass", "123"},
            };
            
            //序列化参数
            var jsonParam = JsonConvert.SerializeObject(dic);

            //发送请求
            var request = (HttpWebRequest)WebRequest.Create(Url);
            request.Method = "POST";
            request.ContentType = "application/json;charset=UTF-8";
            var byteData = Encoding.UTF8.GetBytes(jsonParam);
            var length = byteData.Length;
            request.ContentLength = length;
            var writer = request.GetRequestStream();
            writer.Write(byteData, 0, length);
            writer.Close();

            //接收数据
            var response = (HttpWebResponse)request.GetResponse();
            var responseString = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding("utf-8")).ReadToEnd();

            var url = "xxxxxxxxxxxxxxxxxxxxxx";
            var webClientObj = new WebClient();
            var postVars = new NameValueCollection {
                {"name", "test"},
                {"pass", "123"}
            };

            byte[] byRemoteInfo = webClientObj.UploadValues(url, "POST", postVars);
            string json = Encoding.UTF8.GetString(byRemoteInfo);

var url = "xxxxxxxxxxxxxxxxxxxxxxx";
            //通过抓包工具，可以看到是这个格式
            var postData = "username=test&password=123";

            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
            req.Method = "POST";
            req.Timeout = 30000;
            req.AllowAutoRedirect = false;
            req.ContentType = "application/x-www-form-urlencoded";
            req.KeepAlive = true;

            byte[] postBytes = Encoding.UTF8.GetBytes(postData);
            req.ContentLength = postBytes.Length;
            Stream postDataStream = req.GetRequestStream();
            postDataStream.Write(postBytes, 0, postBytes.Length);
            postDataStream.Close();

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