C#通过浏览器的UserAgent获取Page Source

如题，直接上代码：

HttpWebRequest myReq = (HttpWebRequest)WebRequest.Create(uri);
myReq.UserAgent = "Mozilla/5.0 (compatible; Yahoo! Slurp; http://help.yahoo.com/help/us/ysearch/slurp)";
HttpWebResponse result = (HttpWebResponse)myReq.GetResponse();
Stream receviceStream = result.GetResponseStream();
StreamReader readerOfStream = new StreamReader(receviceStream, System.Text.Encoding.GetEncoding("utf-8"));
string strHTML = readerOfStream.ReadToEnd();
readerOfStream.Close();
receviceStream.Close();
result.Close();
return strHTML;