关于encoding 的问题，问题较多较杂，两天没有头绪。

Question

写一个aps.net 的模拟蜘蛛程序，简单流程搞定了，最关键的 网页编码判断上，
utf -8gb2312bgk。用这种方案，不行
  static string GetHtml(string url, Encoding encoding)
  {
    byte[] buf = new WebClient().DownloadData(url);
    if (encoding != null) return encoding.GetString(buf);
    string html = Encoding.UTF8.GetString(buf);
    encoding = GetEncoding(html);
    if (encoding == null || encoding == Encoding.UTF8) return html;
    return encoding.GetString(buf);
  }
只能区分 utf8 与 非utf8 被否定，而且 encoding 不支持中文的gbk 怎么办？

Answer 1

encoding.getecoding(936)
encoding.default

Answer 2

难道要让我自己写个 encoding 派生类？

Answer 3

public static string GetEncoding(string url)
        {
            HttpWebRequest request = null;
            HttpWebResponse response = null;
            StreamReader reader = null;
            try
            {
                request = (HttpWebRequest)WebRequest.Create(url);
                request.Timeout = 20000;
                request.AllowAutoRedirect = false;                response = (HttpWebResponse)request.GetResponse();
                if (response.StatusCode == HttpStatusCode.OK && response.ContentLength < 1024 * 1024)
                {
                    if (response.ContentEncoding != null && response.ContentEncoding.Equals("gzip", StringComparison.InvariantCultureIgnoreCase))
                        reader = new StreamReader(new GZipStream(response.GetResponseStream(), CompressionMode.Decompress));
                    else
                        reader = new StreamReader(response.GetResponseStream(), Encoding.ASCII);                    string html = reader.ReadToEnd();                    Regex reg_charset = new Regex(@"charset\b\s*=\s*(?<charset>[^""]*)");
                    if (reg_charset.IsMatch(html))
                    {
                        return reg_charset.Match(html).Groups["charset"].Value;
                    }
                    else if (response.CharacterSet != string.Empty)
                    {
                        return response.CharacterSet;
                    }
                    else
                        return Encoding.Default.BodyName;
                }
            }
            catch
            {
            }
            finally
            {                if (response != null)
                {
                    response.Close();
                    response = null;
                }
                if (reader != null)
                    reader.Close();                if (request != null)
                    request = null;            }            return Encoding.Default.BodyName;
        }