C#XmlDocumentをstringに変換

        /// 
       
        /// 
        ///  XmlDocument   string 
        /// /// 
      
        /// ///   
        /// ///    
        public string ConvertXmlToString(XmlDocument xmlDoc)
        {
            MemoryStream stream = new MemoryStream();
            XmlTextWriter writer = new XmlTextWriter(stream, null);
            writer.Formatting = Formatting.Indented; xmlDoc.Save(writer);
            StreamReader sr = new StreamReader(stream, System.Text.Encoding.UTF8);
            stream.Position = 0;
            string xmlString = sr.ReadToEnd();
            sr.Close();
            stream.Close();
            return xmlString;
        }