C#读取网页

public bool getweb(string strURL,out string buf)
  {
   buf="";
   try
   {
    //Uri url=new Uri(strURL,false);
    HttpWebRequest request;
    request = (HttpWebRequest)WebRequest.Create(strURL);
    request.Method="POST"; //Post请求方式
    request.ContentType="text/html;charset=gb2312"; //内容类型
    string paraUrlCoded = System.Web.HttpUtility.UrlEncode(""); //参数经过URL编码
    byte[] payload;
    payload = System.Text.Encoding.GetEncoding("GB2312").GetBytes(paraUrlCoded); //将URL编码后的字符串转化为字节
    request.ContentLength = payload.Length; //设置请求的ContentLength
    Stream writer = request.GetRequestStream(); //获得请求流
    writer.Write(payload,0,payload.Length); //将请求参数写入流
    writer.Close(); //关闭请求流
    HttpWebResponse response;
    response = (HttpWebResponse)request.GetResponse(); //获得响应流
    Stream s;
    s = response.GetResponseStream();
    StreamReader objReader = new StreamReader(s,System.Text.Encoding.GetEncoding("GB2312"));
    string HTML = "";
    string sLine ="";
    int i = 0;
    while (sLine!=null)
    {
     i++;
     sLine = objReader.ReadLine();
     if (sLine!=null)
      HTML += sLine;
    }
    //HTML = HTML.Replace("&lt;","<");
    //HTML = HTML.Replace("&gt;",">");
    buf=HTML;
    return true;
   }
   catch (Exception x)
   {   
    buf=x.Message.ToString();
    return false;    
   }
  }