Authenticate Site Minder using httpwebrequest and httpwebresponse

Question

We are trying to authenticate the site Minder by using httpWebRequest and httpWebResponse and read the cookies. But we are unable to get the cookies

      string url = "https://xxxx/login.jsp";
      string PostData = "USER=" + HttpUtility.UrlEncode("username", Encoding.UTF8) + "&PASSWORD=" + HttpUtility.UrlEncode("passwordval", Encoding.UTF8) + "&rememberMe=" + HttpUtility.UrlEncode("RememberMe", Encoding.UTF8) + "&SMAUTHREASON=" + HttpUtility.UrlEncode("0", Encoding.UTF8) ;
       request = (HttpWebRequest)HttpWebRequest.Create(url);
       request.Method = "POST";
       request.ContentType = "application/x-www-form-urlencoded";          
       request.UserAgent = "Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)";
        request.AllowAutoRedirect = false;
        StreamWriter sr = new StreamWriter(request.GetRequestStream());
        sr.Write(PostData);
        HttpWebResponse loWebResponse = (HttpWebResponse)request.GetResponse();
        using (StreamReader sr1 = new StreamReader(loWebResponse.GetResponseStream()))
        {
            string page1 = sr1.ReadToEnd();
        }
        foreach (Cookie c in loWebResponse.Cookies)
        {
            Console.WriteLine(c.Name + "=" + c.Value);
            Console.WriteLine(c.Domain);
            Console.WriteLine(c);
        }
        Console.ReadLine();

Please advice