public void LoginToUrl(string url,string username, string password )
    {
        formUrl = url;
        formParams = string.Format("username={0}&password={1}", username,password);

        WebRequest req = WebRequest.Create(formUrl.Trim());//
        req.ContentType = "application/x-www-form-urlencoded";
        req.Method = "POST";
          bytes = Encoding.ASCII.GetBytes(formParams);
        req.ContentLength = bytes.Length;
        using (Stream os = req.GetRequestStream())
        {
            os.Write(bytes, 0, bytes.Length);
        }
        WebResponse resp = req.GetResponse();
        cookieHeader = resp.Headers["Set-cookie"];

    }