WebRequest的get及post提交

 static string get_html(string url)
        {
            var request = WebRequest.Create(url);
            var response = request.GetResponse();
            var html = "";
            using (StreamReader sr = new StreamReader(response.GetResponseStream(), Encoding.UTF8))
            {
                html = sr.ReadToEnd();
            }
            return html;
        }

   public static string PostData()
        {
            var html = "";
            var account = "xxxx"; var sign = md5(pwd);
            string postdata = string.Format("Account={0}&Sign={1}",  account,  sign);
            //****************
            HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create("http://localhost:4500/xxxx.ashx");
            httpWebRequest.ContentType = "application/x-www-form-urlencoded";
            httpWebRequest.Method = "POST";
            httpWebRequest.Timeout = ;
            byte[] btBodys = Encoding.UTF8.GetBytes(postdata);
            httpWebRequest.ContentLength = btBodys.Length;
            httpWebRequest.GetRequestStream().Write(btBodys, , btBodys.Length);
            //****************
            var response = httpWebRequest.GetResponse();
            using (StreamReader sr = new StreamReader(response.GetResponseStream(), Encoding.UTF8))
            {
                html = sr.ReadToEnd();
            }
            return html;

        }