请问.net怎么可以在下载页面时，判断编码方式后再下载？如果得不到编码方式的话，网页经常为乱码

Question

我已经用过很多种方式来判断了，但效果都不怎么样？在未知网页的编码方式时，请问怎么才可以正常下载到网页，而不是乱码呢？请大家指教下

        #region【获取网页HTML文本】
        /// <summary>
        /// 获取url网页的HTML文本信息
        /// </summary>
        /// <param name="url">网页URL</param>
        /// <param name="codeType">编码方式</param>
        /// <returns>返回HTML文本字符串</returns>
        public static String GetResponseText(string url, string codeType)
        {
            string responseFromServer = null;
            Stream dataStream = null;
            StreamReader reader = null;
            try
            {
                WebRequest request = WebRequest.Create(url);
                request.Credentials = CredentialCache.DefaultCredentials;
                HttpWebResponse response = (HttpWebResponse)request.GetResponse();
                if (response.StatusDescription == "OK")
                {
                    try
                    {
                        dataStream = response.GetResponseStream();
                        reader = new StreamReader(dataStream, GetPageEncoding(url));
                        responseFromServer = reader.ReadToEnd();
                        Regex rex = new Regex(@"(?<=charset\s*=\s*)[^""]*?(?="")", RegexOptions.IgnoreCase);
                        string charset = rex.Match(responseFromServer, 0).Value;
                        if (!charset.Equals("utf-8")) //如果编码方式不是utf-8的话，则重新用默认方式下载网页
                        {
                            reader = new StreamReader(dataStream, Encoding.Default);
                            responseFromServer = reader.ReadToEnd();
                        }
                    }
                    finally
                    {
                        reader.Close();
                        dataStream.Close();
                    }
                }
                response.Close();
                return responseFromServer;
            }
            catch (Exception ex)
            {
                return ex.Message;
            }

        }
        #endregion