// 要访问的目标页面 

string targetUrl = "http://httpbin.org/ip";

 // 代理服务器(产品官网 www.16yun.cn) 

string proxyHost = "http://t.16yun.cn"; 

string proxyPort = "6447"; 

// 代理隧道验证信息 

string proxyUser = "16IXNGXO";

 string proxyPass = "366338"; 

// 设置代理服务器

 WebProxy proxy = new WebProxy(string.Format("{0}:{1}",

 proxyHost, proxyPort), true);

 ServicePointManager.Expect100Continue = false;

 var request = WebRequest.Create(targetUrl) as HttpWebRequest;

 request.AllowAutoRedirect = true; request.KeepAlive = true;

 request.Method = "GET"; request.Proxy = proxy; 

//request.Proxy.Credentials = CredentialCache.DefaultCredentials;

 request.Proxy.Credentials = new System.Net.NetworkCredential(proxyUser, proxyPass);

 // 设置Proxy Tunnel // Random ran=new Random();

 // int tunnel =ran.Next(1,10000); 

// request.Headers.Add("Proxy-Tunnel", String.valueOf(tunnel));

 //request.Timeout = 20000; //request.ServicePoint.ConnectionLimit = 512;

 //request.UserAgent = "Mozilla/5.0 (Windows NT 6.3; Win64; x64)

 AppleWebKit/537.36 (KHTML, like Gecko) Chrome/48.0.2564.82 Safari/537.36"; 

//request.Headers.Add("Cache-Control", "max-age=0"); 

//request.Headers.Add("DNT", "1");

 //String encoded = System.Convert.ToBase64String(System.Text.Encoding.GetEncoding("ISO-8859-1").

GetBytes(proxyUser + ":" + proxyPass)); 

//request.Headers.Add("Proxy-Authorization", "Basic " + encoded); 

using (var response = request.GetResponse() as HttpWebResponse) 

using (var sr = new StreamReader(response.GetResponseStream(), Encoding.UTF8)) 

{ string htmlStr = sr.ReadToEnd(); }