读取Internet网站上的某些内容

当需要用到某个网站上的一些内容时，可以使用下面的方法，获取整个网页的内容，然后在截取自己想要的那部分

private string GetWebContent(string Url)
{
            string strResult = "";
            try
            {

　　　　　 //声明一个HttpWebRequest请求

　　　　　 HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
                //设置连接超时时间
               request.Timeout = 30000;
                request.Headers.Set("Pragma", "no-cache");
                //这个一定要加上，在某些网站没有会发生"远程服务器返回错误: (403) 已禁止。"错误
                request.UserAgent = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; QQWubi 133; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; CIBA; InfoPath.2)";
                //rq.Accept = "*/*";
                //rq.Accept = "image/jpeg, application/x-ms-application, image/gif, application/xaml+xml, image/pjpeg, application/x-ms-xbap, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/x-shockwave-flash, */*";
                request.Method = "GET";
                HttpWebResponse response = (HttpWebResponse)request.GetResponse();
                Stream streamReceive = response.GetResponseStream();
                Encoding encoding = Encoding.GetEncoding("GB2312");
                StreamReader streamReader = new StreamReader(streamReceive, encoding);
                strResult = streamReader.ReadToEnd();
            }
            catch(Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            return strResult;
}