C#调用接口Post提交数据 application/x-www-form-urlencoded 方式

string EndResult = "";
            string SendMessageAddress = "URL";
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(SendMessageAddress);
            request.Method = "POST";
            request.AllowAutoRedirect = true;
            request.Timeout = 20 * 1000;
            request.ContentType = "application/x-www-form-urlencoded";
            request.Headers.Add("x-cherun-auth-key", "LarxMbndsxfGwoYAqsfJSPPU42l04cb3");
            string PostData = "a=1&b=2";
            byte[] byteArray = Encoding.Default.GetBytes(PostData);
            request.ContentLength = byteArray.Length;
            using (Stream newStream = request.GetRequestStream())
            {
                newStream.Write(byteArray, 0, byteArray.Length);//写入参数
                newStream.Close();
            }

            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            Stream rspStream = response.GetResponseStream();
            using (StreamReader reader = new StreamReader(rspStream, Encoding.UTF8))
            {
                EndResult = reader.ReadToEnd();
                rspStream.Close();
            }
            response.Close();