如何檢查是否登錄失敗

下面的代碼已被提琴手產生的，被稱爲在button_Click事件。如何檢查是否登錄失敗

//Create request to URL. 
HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://forums.codeguru.com/login.php?do=login"); 

//Set request headers. 
request.UserAgent = "Mozilla/5.0 (Windows NT 5.1; rv:19.0) Gecko/20100101 Firefox/19.0"; 
request.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"; 
request.Headers.Set(HttpRequestHeader.AcceptLanguage, "en-US,en;q=0.5"); 
request.Headers.Set(HttpRequestHeader.AcceptEncoding, "gzip, deflate"); 
request.Referer = "http://forums.codeguru.com/"; 
request.KeepAlive = false; 
request.ContentType = "application/x-www-form-urlencoded"; 

//Set request method 
request.Method = "POST"; 

// Disable 'Expect: 100-continue' behavior. More info: http://haacked.com/archive/2004/05/15/http-web-request-expect-100-continue.aspx 
      request.ServicePoint.Expect100Continue = false; 

//Set request body. 

**// Fail** 
    string body = @"vb_login_username=**userid**&vb_login_password=&vb_login_password_hint=Password&s=&securitytoken=guest&do=login&vb_login_md5password=a35cef11bdd55e36423f8d3b1ed69dea&vb_login_md5password_utf=a35cef11bdd55e36423f8d3b1ed69dea"; 

    byte[] postBytes = System.Text.Encoding.UTF8.GetBytes(body); 
    request.ContentLength = postBytes.Length; 
    Stream stream = request.GetRequestStream(); 
    stream.Write(postBytes, 0, postBytes.Length); 
    stream.Close(); 

//Get response to request. 
response = (HttpWebResponse)request.GetResponse(); 
Stream responseStream = response.GetResponseStream(); 

var reader = new System.IO.StreamReader(responseStream, Encoding.UTF8); 
string srcString = reader.ReadToEnd(); 

} 
catch (WebException e) 
{ 
      //ProtocolError indicates a valid HTTP response, but with a non-200 status code (e.g. 304 Not Modified, 404 Not Found) 
      if (e.Status == WebExceptionStatus.ProtocolError) response = (HttpWebResponse)e.Response; 
      else return false; 
} 
catch (Exception) 
{ 
      if (response != null) response.Close(); 
      return false; 
} 

return true;

}

代碼在button_Click事件

 HttpWebResponse response; 

     if (Request_forums_codeguru_com(out response)) 
     { 
      //Success, possibly use response. 

      HttpStatusCode status = response.StatusCode; 

      // Status is alway OK 

      response.Close(); 

      MessageBox.Show("Succesful login"); 

     } 
     else 
     { 
      //Failure, cannot use response. 

      MessageBox.Show("Unsuccesful login"); 
     }

但是即使我輸入了錯誤的密碼，我得到的HTTPStatus爲OK。我如何檢查登錄失敗。

在最後的階段，我將在Python服務器接收數據，因此，上述只是測試。

編輯：

當用戶輸入了錯誤的用戶名/密碼組合，他/她會看到以下內容： -

Wrong User id/Password combination