将数据作为字符串返回时，XML格式不会出现在wcf中

Function:

public string getAccomodationspattern2(string AccomodationID)
        {
            SqlCommand cmd = new SqlCommand("XML_AccommodationsDetail_V4", con);

            cmd.Parameters.AddWithValue("@AccommodationID", AccomodationID);

            cmd.CommandType = CommandType.StoredProcedure;

            SqlDataAdapter da = new SqlDataAdapter(cmd);

            DataTable dt = new DataTable();

            da.Fill(dt);
            for (int j = 0; j < dt.Rows.Count; j++)
            {
                for (int k = 0; k < dt.Columns.Count; k++)
                {
                    Response += dt.Rows[j][k].ToString();
                }
            }

            //StringBuilder output = new StringBuilder();
            //XmlReader rawData  = XmlReader.Create(new StringReader(Response));

            //XmlWriterSettings writerSettings = new XmlWriterSettings();
            //writerSettings.OmitXmlDeclaration = true;

            //using (XmlWriter transformedData = XmlWriter.Create(output, writerSettings))
            //{
            //    XslCompiledTransform transform = new XslCompiledTransform();
            //    transform.Load(HttpContext.Current.Server.MapPath("getaccommodation2.xslt"));
            //    transform.Transform(rawData, transformedData);
            //    return output.ToString();
            //}

            XslCompiledTransform transform = new XslCompiledTransform();

            transform.Load(HttpContext.Current.Server.MapPath("getaccommodation2.xslt"));

            StringWriter results = new StringWriter();

            using (XmlReader reader = XmlReader.Create(new StringReader(Response)))
            {
                transform.Transform(reader, null, results);
            }
            return results.ToString();
            //XDocument xdoc = new XDocument(results.ToString());
            //return xdoc.Root;

        }
public string getAccomodationspatte