public  string GetHtml(string url, byte[] postData, bool isPost, CookieContainer cookieContainer,string refurl)
        {
            ServicePointManager.Expect100Continue = false;

Thread.Sleep(NetworkDelay);//等待

currentTry++;

HttpWebRequest httpWebRequest = null;
           
            HttpWebResponse httpWebResponse = null;
            try
            {
               // byte[] byteRequest = Encoding.Default.GetBytes(postData);
                byte[] byteRequest = postData;
                httpWebRequest = (HttpWebRequest)HttpWebRequest.Create(url);
                if (Proxy != null)
                    httpWebRequest.Proxy = Proxy;      //代理服务器设置
                httpWebRequest.CookieContainer = cookieContainer;
                httpWebRequest.ContentType = contentType;
                httpWebRequest.ServicePoint.ConnectionLimit = maxTry;
                httpWebRequest.Referer = refurl;
                httpWebRequest.Accept = accept;
                httpWebRequest.UserAgent = userAgent;
                httpWebRequest.Method = isPost ? "POST" : "GET";
                httpWebRequest.ContentLength = byteRequest.Length;

Stream stream = httpWebRequest.GetRequestStream();
                stream.Write(byteRequest, 0, byteRequest.Length);
                stream.Close();

httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse();
                Stream responseStream = httpWebResponse.GetResponseStream();
                StreamReader streamReader = new StreamReader(responseStream, encoding);
                string html = streamReader.ReadToEnd();
                streamReader.Close();
                responseStream.Close();
                currentTry = 0;

httpWebRequest.Abort();
                httpWebResponse.Close();
                foreach (Cookie cookie in httpWebResponse.Cookies)
                {
                    cookieContainer.Add(cookie);
                }

return html;
            }
            catch (Exception)
            {

if (httpWebRequest != null)
                {
                    httpWebRequest.Abort();
                } if (httpWebResponse != null)
                {
                    httpWebResponse.Close();
                }
                return "";
            }
        }

代理服务器都已经淘汰的技术，没想到现在还有人用。但是吃一堑长一智。希望可以帮到你们。