request.GetResponse (500) 内部服务器错误
 private string GetWebForm(string url, string data, CookieContainer myCookieContainer)   //提交表单,获取登陆返回信息
        {
            HttpWebRequest request;
            HttpWebResponse response;
            request = (HttpWebRequest)WebRequest.Create(url);
            request.Method = "POST";
            request.ContentType = "application/x-www-form-urlencoded";
            request.CookieContainer = myCookieContainer;  //设置cookie

            //注意参数为中文时需要编码
            //System.Web.HttpUtility.UrlEncode("搜 索", Encoding.GetEncoding("gb2312"));          
            byte[] byteRequest = Encoding.GetEncoding("gb2312").GetBytes(data);
            request.ContentLength = byteRequest.Length;
            Stream stream = request.GetRequestStream();
            stream.Write(byteRequest, 0, byteRequest.Length);
            stream.Close();
            response = (HttpWebResponse)request.GetResponse();  //这句500错误
            //try
            //{
            //    response = (HttpWebResponse)request.GetResponse();
            //}
            //catch (WebException ex)
            //{
            //    response = (HttpWebResponse)ex.Response;
            //}
            StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding("UTF-8"));
            string Msg = reader.ReadToEnd();
            stream.Dispose();
            reader.Dispose();
            return Msg;
        }
调用：
CookieContainer myCookieContainer = new CookieContainer();
            string url = "http://180.166.7.150:8880/captcha.do?phoneNumber=13018917111&province