网页抓取,该如何解决

private string GetContentFromUrll(string _requestUrl)        {            string _StrResponse ="";            HttpWebRequest _WebRequest = ( HttpWebRequest )WebRequest.Create( _requestUrl );            _WebRequest.Method = "GET";            WebResponse _WebResponse = _WebRequest.GetResponse();            StreamReader _ResponseStream = new StreamReader( _WebResponse.GetResponseStream(), System.Text.Encoding.GetEncoding("gb2312"));            _StrResponse = _ResponseStream.ReadToEnd();            _WebResponse.Close();             _ResponseStream.Close();            return _StrResponse;                }