请教(新浪模拟登录)

 private void SinaLogin_Load(object sender, EventArgs e)

        {

            string username = "";

            string password = "";

            string url = "http://login.sina.com.cn/sso/prelogin.php?entry=miniblog&callback=sinaSSOController.preloginCallBack&user=" + username + "&client=ssologin.js(v1.3.12)";

            url = GetUrl(url);

            try

            {

                if (!string.IsNullOrEmpty(url))

                {

                    int a = url.LastIndexOf(',') - 10;

                    int b = url.LastIndexOf(':') + 2;

                    string servertime = url.Substring(a, 10);

                    string nonce = url.Substring(b, 6);

                    string Pwd1 = GetPwd(password);

                    string Pwd2 = GetPwd(Pwd1);

                    string Pwd3 = GetPwd(Pwd2 + servertime + nonce);

                    string login = @"http://login.sina.com.cn/sso/login.php?client=ssologin.js(v1.3.12)&service:miniblog&client:ssologin.js%28v1.3.12%29&entry:miniblog&encoding:utf-8&gateway:1&savestate:0&useticket:1&username:" + username + "&servertime:" + servertime + "&nonce:" + nonce + "&pwencode:wsse&password:"+Pwd3+"&url:http://www.baidu.com&returntype:META&ssosimplelogin:1";

                    string result = GetUrl(login);

                }

                else

                {

                    Console.WriteLine("出错了！");

                }

            }

            catch (Exception)

            {

                

                throw;

            }

           



        }

        static string GetPwd(string Pwd)

        {

            byte[] data = System.Text.Encoding.Default.GetBytes(Pwd);//以字节方式存储

            System.Security.Cryptography.SHA1 sha1 = new System.Security.Cryptography.SHA1CryptoServiceProvider();

            byte[] result = sha1.ComputeHash(data);//得到哈希值

            return System.BitConverter.ToString(result).Replace("-", ""); //转换成为字符串的显示

        }



        private string GetUrl(string url)

        {

            string _str = string.Empty;

            WebRequest request = WebRequest.Create(url);

            

            request.Timeout = 5000;

            //request.Method = "POST";

            try

            {

              WebResponse response = request.GetResponse();



                StreamReader reader = new StreamReader(response.GetResponseStream(),System.Text.Encoding.GetEncoding("gb2312"));

                _str = reader.ReadToEnd();

                reader.Close();

                reader.Dispose();

                response.Close();



            }

            catch (System.Net.WebException ex)

            {

                //tb.Text = ex.Message;

            }

            return _str;

        }