抓取爬虫自动登录

public String Post(string url, string postData)
{
            try
            {
                #region 登录
                string loginurl = "http://10.16.230.26:8080/login.aspx?ReturnUrl=%2flogout.aspx";
                byte[] loginByteArray = Encoding.UTF8.GetBytes(GetLoginPostData()); // 转化 
                CookieContainer myCookieContainer = new CookieContainer();
                //新建一个CookieContainer来存放Cookie集合 
                HttpWebRequest myHttpWebRequest = (HttpWebRequest)WebRequest.Create(loginurl);
                //新建一个HttpWebRequest 
                myHttpWebRequest.ContentType = "application/x-www-form-urlencoded";
                myHttpWebRequest.ContentLength = loginByteArray.Length;
                myHttpWebRequest.Method = "POST";
                myHttpWebRequest.CookieContainer = myCookieContainer;
                //设置HttpWebRequest的CookieContainer为刚才建立的那个myCookieContainer 
                Stream myRequestStream = myHttpWebRequest.GetRequestStream();
                // Send the data. 
                myRequestStream.Write(loginByteArray, 0, loginByteArray.Length); //写入参数 
                myRequestStream.Close();
                //把数据写入HttpWebRequest的Request流 
                myRequestStream.Close();
                //关闭打开对象 
                HttpWebResponse myHttpWebResponse = (HttpWebResponse)myHttpWebRequest.GetResponse();
                //新建一个HttpWebResponse 
                myHttpWebResponse.Cookies = myCookieContainer.GetCookies(myHttpWebRequest.RequestUri);
                //获取一个包含url的Cookie集合的CookieCollection 
                Stream myResponseStream = myHttpWebResponse.GetResponseStream();
                StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.UTF8);
                //把数据从HttpWebResponse的Response流中读出 
                myStreamReader.Close();
                myResponseStream.Close();
                #endregion

                byte[] byteArray = Encoding.UTF8.GetBytes(postData); // 转化 

                //拿到了Cookie，再进行请求就能直接读取到登录后的内容了 
                myHttpWebRequest = (HttpWebRequest)WebRequest.Create(url);
                myHttpWebRequest.Headers.Add("Accept-Language:   zh-cn");
                myHttpWebRequest.Headers.Add("UA-CPU:   x86");
                myHttpWebRequest.Headers.Add("Accept-Encoding:   gzip, deflate");
                myHttpWebRequest.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1;  Embedded Web Browser from: http://bsalsa.com/; InfoPath.2; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022)";
                myHttpWebRequest.ContentType = "application/x-www-form-urlencoded";
                myHttpWebRequest.ContentLength = byteArray.Length;
                myHttpWebRequest.Method = "POST";
                myHttpWebRequest.CookieContainer = myCookieContainer;//* 
                //刚才那个CookieContainer已经存有了Cookie,把它附加到HttpWebRequest中则能直接通过验证 

                myRequestStream = myHttpWebRequest.GetRequestStream();
                // Send the data. 
                myRequestStream.Write(byteArray, 0, byteArray.Length); //写入参数 
                myRequestStream.Close();

                myHttpWebResponse = (HttpWebResponse)myHttpWebRequest.GetResponse();
                myHttpWebResponse.Cookies = myCookieContainer.GetCookies(myHttpWebRequest.RequestUri);
                myResponseStream = myHttpWebResponse.GetResponseStream();
                myStreamReader = new StreamReader(myResponseStream, Encoding.UTF8);
                string outdata = myStreamReader.ReadToEnd();
                myStreamReader.Close();
                myResponseStream.Close();
                return outdata;
            }
            catch (Exception ex)
            {
                return String.Empty;
            }
}