string url = "http://new.cnzz.com/v1/login.php?siteid=******";
        string postData = "password=******";
        string outdata = "";
        string contentType = "application/x-www-form-urlencoded";
        string accept = "image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/x-ms-application, application/x-ms-xbap, application/vnd.ms-xpsdocument, applicat";
        string userAgent = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.2; Trident/4.0; EmbeddedWB 14.52 from: http://www.bsalsa.com/ EmbeddedWB 14.52; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022; .NET";
        private void button1_Click(object sender, EventArgs e)
        {
            byte[] byteRequest = Encoding.GetEncoding("gb2312").GetBytes(postData);  
            HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);
            //request.CookieContainer = cookieContainer;
            request.Referer = url;
            request.ContentType = contentType ;
            request.ContentLength = byteRequest.Length;  //附加信息长度
            request.Accept = accept;
            request.UserAgent = userAgent;
            request.Method = "POST";

            Stream streamWrite = request.GetRequestStream();
            streamWrite.Write(byteRequest, 0, byteRequest.Length);
            streamWrite.Close();

            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            Stream streamRead = response.GetResponseStream();  //转换为数据流
            StreamReader reader = new StreamReader(streamRead, Encoding.GetEncoding("gb2312"));
            string html=reader.ReadToEnd();   //通过StreamReader类读取流
            reader.Close();
           streamRead.Close();