c#抓取网页内容出现乱码
我做了如下代码读取网页内容，但在分析不同编码的网页时，出现乱码
//取得HTML源码
  private string getHtmlInfo(string urlSelet)
  {
  string strResult = "";
  if(urlSelet.Equals(""))
  return strResult = "";
  //HTML源码
  Console.WriteLine("**********************=" + urlSelet);
  try
  {
  //声明一个HttpWebRequest请求 
  HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(urlSelet);
  webRequest.Method = "GET";
  webRequest.UserAgent = "Opera/9.25 (Windows NT 6.0; U; en)";
  HttpWebResponse webResponse = (HttpWebResponse)webRequest.GetResponse();
  //Encoding encoding = Encoding.GetEncoding("GB2312");
  //取得要取得的网页的编码方式
  Encoding encoding = GetEncoding(webResponse);
  using (System.IO.Stream stream = webResponse.GetResponseStream())
  {
  using (System.IO.StreamReader reader = new StreamReader(stream,encoding))
  {
  strResult = reader.ReadToEnd();
  }
  }
  }
  catch (Exception exp)
  {
   
  MessageBox.Show("出错:" + exp.Message);

  }
  return strResult;
  }
//取得要取得的网页的编码方式
 public Encoding GetEncoding(HttpWebResponse response) 
  { 
  Encoding code = Encoding.Default;
  string charset = null;
  //如果发现content-type头  
  string ctypeLower = response.Headers["content-type"];
  string ctypeOrder = response.Headers["Content-Type"];
  string ctype="";
  if (!ctypeLower.Equals(""))
  ctype = ctypeLower;
  if (!ctypeOrder.Equals(""))
  ctype = ctypeOrder;
  Console.WriteLine("ctype:" + ctype);
  if (ctype != null)
  {
  int ind = ctype.IndexOf("charset=");
  if (ind != -1)
  {
  charset = ctype.ToLower().Substring(ind + 8);
  }
  }
  Console.WriteLine("charset编码格式:" + charset);
  if (charset != "") 
  { 
  try 
  {
  code = Encoding.GetEncoding(charset); 
  } 
  catch{} 
  }
  return code; 
 } 

发现取网页编码时有时能取到，有时去不到，所以还会有显示乱码问题
请求哪位大侠帮我一下

------解决方案--------------------
今天下午抽时间研究了一下这个页面:
http://www.dunsh.org/forums/thread-984-1-1.html
实际上页面返回的HTTP如下：
HTTP/1.1 200 OK
Proxy-Connection: close
Connection: close
Content-Length: 33906
Via: 1.1 MSSZISA02
Date: Thu, 03 Dec 2009 08:02:37 GMT
Content-type: text/html
Server: Microsoft-IIS/6.0
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X-Powered-By: PHP/5.2.9-1
Set-Cookie: cdb_sid=plpmwC; expires=Thu, 10-Dec-2009 08:02:37 GMT; path=/
Set-Cookie: cdb_oldtopics=D984D; expires=Thu, 03-Dec-2009 09:02:37 GMT; path=/
Set-Cookie: cdb_visitedfid=9; expires=Sat, 02-Jan-2010 08:02:37 GMT; path=/