HTML格式化为标准XML

returns></returns>         private static XElement Html2XML(string html)         {             Sgml.SgmlReader sgmlReader = new Sgml.SgmlReader();             sgmlReader.DocType = "HTML";             sgmlReader.WhitespaceHandling = WhitespaceHandling.All;             sgmlReader.CaseFolding = Sgml.CaseFolding.ToLower;             sgmlReader.InputStream = new StringReader(html);             return XElement.Load(sgmlReader);