Авторизация на сайте Cookie - C#

Request URL:http://xxxx.biz/login/login
Request Method:POST
Status Code:303 See Other
Remote Address:176.9.136.59:80
 
Response Headers
HTTP/1.1 303 See Other
Server: nginx
Date: Sun, 08 May 2016 04:24:59 GMT
Content-Type: text/html;charset=UTF-8
Content-Length: 0
Connection: keep-alive
Cache-control: private, max-age=0
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Last-Modified: Sun, 08 May 2016 04:24:59 GMT
Location: http://xxxx.biz/
Set-Cookie: xf_user=1%2C594a06e721ac2dc1dcc7714cfbeddd89f064d025; expires=Tue, 07-Jun-2016 04:24:58 GMT; path=/; httponly
Set-Cookie: xf_session=6c13ff2937edee51043df5eb61594a67; path=/; httponly
X-Frame-Options: SAMEORIGIN
X-Powered-By: PHP/5.3.3
X-Robots-Tag: none
 
Request Headers
POST /login/login HTTP/1.1
Host: ojrs243un5zgkltcnf5a.cmle.ru
Connection: keep-alive
Content-Length: 114
Cache-Control: max-age=0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Origin: http://ojrs243un5zgkltcnf5a.cmle.ru
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.94 Safari/537.36
Content-Type: application/x-www-form-urlencoded
Referer: http://xxxx.biz/
Accept-Encoding: gzip, deflate
Accept-Language: ru-RU,ru;q=0.8,en-US;q=0.6,en;q=0.4
Cookie: crtg_rta=; _gat=1; xf_session=d8719b6c9692ab795b6ae3c45dfd24d8; _ga=GA1.2.783234481.1460544443
 
Form Data
login=admin&register=0&password=XXXXXX&remember=1&cookie_check=1&_xfToken=&redirect=http%3A%2F%2Fxxxx.biz%2F

WebRequest request = WebRequest.Create("http://xxx.biz/login/login");
                request.Method = "POST";
                string postData = "login=admin&register=0&password=xxxxxxxxx&remember=1&cookie_check=1&_xfToken=&redirect=http%3A%2F%2Fxxxx.biz%2F";
                byte[] byteArray = Encoding.GetEncoding("windows-1251").GetBytes(postData);
                request.ContentType = "application/x-www-form-urlencoded";
                request.ContentLength = byteArray.Length;
                Stream dataStream = request.GetRequestStream();
                dataStream.Write(byteArray, 0, byteArray.Length);
                dataStream.Close();
                WebResponse response = request.GetResponse();
                dataStream = response.GetResponseStream();
                StreamReader reader = new StreamReader(dataStream);
                string responseFromServer = reader.ReadToEnd();
                //MessageBox.Show(responseFromServer);
                textBox1.Text = responseFromServer;
                reader.Close();
                dataStream.Close();
                response.Close();

 WebRequest request = WebRequest.Create(textBox6.Text);
                request.Method = "POST";
                string nam = WebUtility.UrlEncode(name[i]);
                string mes = WebUtility.UrlEncode(message[i]);
                string postData = "_guestUsername=" + nam + "&message_html=" + mes + "&_xfRelativeResolver=" + textBox6.Text + "%2Freply&_xfToken=&_xfRequestUri=%2Fthreads%2Fxxxx.1470%2Freply&_xfNoRedirect=1&_xfResponseType=json";
                //_guestUsername=nam&message_html=" + mes + "&_xfRelativeResolver=" + textBox6.Text + "%2Freply&_xfToken=&_xfRequestUri=%2Fthreads%2Fxxxx.1470%2Freply&_xfNoRedirect=1&_xfResponseType=json
                byte[] byteArray = Encoding.GetEncoding("windows-1251").GetBytes(postData);
                request.ContentType = "application/x-www-form-urlencoded";
                request.ContentLength = byteArray.Length;
                Stream dataStream = request.GetRequestStream();
                dataStream.Write(byteArray, 0, byteArray.Length);
                dataStream.Close();
                WebResponse response = request.GetResponse();
                dataStream = response.GetResponseStream();
                StreamReader reader = new StreamReader(dataStream);
                string responseFromServer = reader.ReadToEnd();
                reader.Close();
                dataStream.Close();
                response.Close();