C#HttpWebRequest设置代理IP访问网页

public String sendpost(String phonenumber)
{
WebProxy proxyObject = new WebProxy("114.212.12.4", 3128);//str为IP地址 port为端口号
HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://reg.email.163.com/unireg/call.do?cmd=added.mobilemail.checkBinding");
request.Proxy = proxyObject; //设置代理 
CookieContainer cookieContainer = new CookieContainer();
request.CookieContainer = cookieContainer;

CookieContainer cookie = request.CookieContainer;//如果用不到Cookie，删去即可
//以下是发送的http头，随便加，其中referer挺重要的，有些网站会根据这个来反盗链
request.Referer = "http://reg.email.163.com/unireg/call.do?cmd=register.entrance&from=126mail";
request.Accept = "Accept:text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
request.Headers["Accept-Language"] = "zh-CN,zh;q=0.";
request.Headers["Accept-Charset"] = "GBK,utf-8;q=0.7,*;q=0.3";
request.UserAgent = "User-Agent:Mozilla/5.0 (Windows NT 5.1) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/14.0.835.202 Safari/535.1";
request.KeepAlive = true;
//上面的http头看情况而定，但是下面俩必须加
request.ContentType = "application/x-www-form-urlencoded";
request.Method = "POST";

Encoding encoding = Encoding.UTF8;//根据网站的编码自定义
string postDataStr = "mobile=" + phonenumber;
byte[] postData = encoding.GetBytes(postDataStr);
request.ContentLength = postData.Length;
Stream requestStream = request.GetRequestStream();
requestStream.Write(postData, 0, postData.Length);

HttpWebResponse response = (HttpWebResponse)request.GetResponse();
Stream responseStream = response.GetResponseStream();
//如果http头中接受gzip的话，这里就要判断是否为有压缩，有的话，直接解压缩即可
if (response.Headers["Content-Encoding"] != null && response.Headers["Content-Encoding"].ToLower().Contains("gzip"))
{
responseStream = new GZipStream(responseStream, CompressionMode.Decompress);
}

StreamReader streamReader = new StreamReader(responseStream, encoding);
string retString = streamReader.ReadToEnd();

streamReader.Close();
responseStream.Close();
return retString;
}