public void GetFunction()
        {
            string serviceAddress = "http://222.111.999.444:8687/tttr/usercrd/12/b7e50cb45a?userid=9999";
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(serviceAddress);
            request.Method = "GET";
            request.ContentType = "text/html;charset=UTF-8";
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            Stream myResponseStream = response.GetResponseStream();
            StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.UTF8);
            string retString = myStreamReader.ReadToEnd();
            myStreamReader.Close();
            myResponseStream.Close();
            Response.Write(retString);
        }

        2.post方法调用接口获取json文件内容
        public void PostFunction()
        {

            string serviceAddress = "http://222.111.999.444:8687/tttr/usercrd/uuu/12/dfd7e4";
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(serviceAddress);

            request.Method = "POST";
            request.ContentType = "application/json";
            string strContent = @"{ ""mmmm"": ""89e"",""nnnnnn"": ""0101943"",""kkkkkkk"": ""e8sodijf9""}";
            using (StreamWriter dataStream = new StreamWriter(request.GetRequestStream()))
            {
                dataStream.Write(strContent);
                dataStream.Close();
            }
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            string encoding = response.ContentEncoding;
            if (encoding == null || encoding.Length < 1)
            {
                encoding = "UTF-8"; //默认编码  
            }
            StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding(encoding));
            string retString = reader.ReadToEnd();
            //解析josn
            JObject jo = JObject.Parse(retString);
            Response.Write(jo["message"]["mmmm"].ToString());
          
        } 

 转载：https://www.cnblogs.com/lchsirblog/p/7239956.html