C#如何使用HttpWebRequest、HttpWebResponse模拟浏览器抓取网页内容

public string GetHtml(string url, Encoding ed)         {             string Html = string.Empty;//初始化新的webRequst             HttpWebRequest Request = (HttpWebRequest)WebRequest.Create(url);              Request.KeepAlive = true;             Request.ProtocolVersion = HttpVersion.Version11;             Request.Method = "GET";             Request.Accept = "*/* ";             Request.UserAgent = "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.56 Safari/536.5";             Request.Referer = url;              HttpWebResponse htmlResponse = (HttpWebResponse)Request.GetResponse();             //从Internet资源返回数据流             Stream htmlStream = htmlResponse.GetResponseStream();             //读取数据流             StreamReader weatherStreamReader = new StreamReader(htmlStream, ed);             //读取数据             Html = weatherStreamReader.ReadToEnd();             weatherStreamReader.Close();             htmlStream.Close();             htmlResponse.Close();             //针对不同的网站查看html源文件             return Html;         }          public string GetHtml(string url)         {             return GetHtml(url, Encoding.UTF8);         }