HttpWebRequest乱码有关问题

HttpWebRequest乱码问题?
HttpWebRequest rqst = (HttpWebRequest)WebRequest.Create(Url);
  HttpWebResponse rsps = (HttpWebResponse)rqst.GetResponse();
  Stream sm = rsps.GetResponseStream();
  s = new StreamReader(sm, Encoding.GetEncoding("")).ReadToEnd();
  return s;

href=ClassList.aspx?classcode=200002&ClassName=鏈嶈?淇℃伅&page=163>最后页　只有classname参数后才出现乱码？请问如何解决？

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C# code

s = new StreamReader(sm, Encoding.GetEncoding("")).ReadToEnd(); 把以上这段代码改成s = new StreamReader(sm, System.Text.Encoding.Default).ReadToEnd();