Test.HttpHeader header = new Test.HttpHeader();
            header.accept = "itext/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
            header.contentType = "application/x-www-form-urlencoded";
            header.method = "POST";
            header.userAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022)";
            header.maxTry = 300;

CookieCollection mycookie = Test.HTMLHelper.GetCookieCollection("http://www.renren.com/PLogin.do",
            //                   "mail=bgaidu%40163.com&password=123456789&origURL=https%3A%2F%2Fsafe.renren.com%2F&domain=renren.com&formName=&method=&isplogin=true&submit=%E7%99%BB%E5%BD%95", header);

  


 HttpWebRequest request = null;
            HttpWebResponse response = null;
            try
            {
                CookieContainer cc = new CookieContainer();
                request = (HttpWebRequest)WebRequest.Create(loginUrl);
                request.Method = header.method;
                request.ContentType = header.contentType;
                byte[] postdatabyte = Encoding.UTF8.GetBytes(postdata);
                request.ContentLength = postdatabyte.Length;
                request.AllowAutoRedirect = false;
                request.CookieContainer = cc;
                request.KeepAlive = true;

                //提交请求
                Stream stream;
                stream = request.GetRequestStream();
                stream.Write(postdatabyte, 0, postdatabyte.Length);
                stream.Close();

                //接收响应
                response = (HttpWebResponse)request.GetResponse();
                response.Cookies = request.CookieContainer.GetCookies(request.RequestUri);

                CookieCollection cook = response.Cookies;
                //Cookie字符串格式
                string strcrook = request.CookieContainer.GetCookieHeader(request.RequestUri);

                return cook;
            }
            catch (Exception ex)
            {

                throw ex;
            }