c#模拟网页自动登录的一段代码，遇到了问题

  using System;
  using System.Collections.Generic;
  using System.Text;
  using System.IO;
  using System.Net;

namespace MyLogin
{
    class PostGetWebRequest
    {

        public string LoginUrl;
      //  private CookieContainer MyCookieContainer;
        private HttpWebRequest request;
        private HttpWebResponse response;
        private Stream stream;
        private StreamReader streamReader;
        private string Src = "";
        private string postData;
        public string HtmlUserName;
        public string HtmlPassword;
       // private string HtmlSubmit;
        public string PostWebRequest()
        {
            request = (HttpWebRequest)WebRequest.Create(LoginUrl);

            MyCookieContainer = new CookieContainer();

            //设置提交相关参数
            postData = "email=" + HtmlUserName.Replace("@", "%40") + "&password=" + HtmlPassword + "&origURL=" + LocationUrl + "&domain=renren.com";

            ASCIIEncoding encoding = new ASCIIEncoding();
            byte[] data = encoding.GetBytes(postData);
            request.Method = "POST";
            request.ContentType = "application/x-www-form-urlencoded";
            request.ContentLength = data.Length;
            request.KeepAlive = false;
            request.CookieContainer = MyCookieContainer;//把取服务器发给客户端跟session 想对应的cookie；相当于是一个容器

            //提交请求
            stream = request.GetRequestStream();
            stream.Write(data, 0, data.Length);
            stream.Close();

            //接收
            response = (HttpWebResponse)request.GetResponse();
            streamReader = new StreamReader(response.GetResponseStream(), Encoding.UTF8);

            Src = streamReader.ReadToEnd();
            streamReader.Close();
            stream.Close();
            return Src;
        }

    }
    class Program
    {
        static void Main(string[] args)
        {
            PostGetWebRequest postGetWebRequest = new PostGetWebRequest();// 没有验证码的网站，登录页面html格式，客户端的
            postGetWebRequest.HtmlUserName = "xxx@163.com";
            postGetWebRequest.HtmlPassword = "aaaaaa";
            postGetWebRequest.LoginUrl = "http://www.renren.com/PLogin.do";//这个是人人的登录页

            string content1 = postGetWebRequest.PostWebRequest();
            Console.WriteLine( content1);
            Console.ReadKey();
        }
    }
}
问题是我想获得post后响应的正文比如 {"code":true,"homeUrl":"http://www.renren.com/callback.do?t=35466507bb49807292e00bbe5063b9090&origURL=http%3A%2F%2Fwww.renren.com%2Fhome&needNotify=false"}
我该怎么修改代码？？ --------------------编程问答-------------------- 什么意思，content1 不是返回的内容吗，如果想post其他地址，就修改url那个网站需要提交的参数，每个页面的参数可能不一样，你先抓包看看都提交了哪些，自己对着组织 --------------------编程问答-------------------- 我运行后返回了一段登录前页面的源代码，但我无法判断是否登录成功啊，如果我能得到post的响应正文就可以，问题是怎么获得？ --------------------编程问答-------------------- {"code":true,"homeUrl":"http://www.renren.com/callback.do?t=35466507bb49807292e00bbe5063b9090&origURL=http%3A%2F%2Fwww.renren.com%2Fhome&needNotify=false"}这是登录成功的

{"catchaCount":1,"code":false,"homeUrl":"http://www.renren.com/SysHome.do?origURL=http%3A%2F%2Fwww.renren.com%2Fhome&catchaCount=1&failCode=128","failDescription":"您的用户名和密码不匹配","failCode":128,"email":"18986143802"}这是登录失败的
我该怎么获取这段代码？

补充：.NET技术 ,  C#