如何让WebServer返回指定XML内容

/*menulist 类开始*/

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Xml;
using Singcn.SQL;
using System.Data.SqlClient;
using System.IO;
using System.Text;

namespace myfunc.Common
{
    /// <summary>
    /// PubFunc 的摘要说明
    /// </summary>
    public class menulist

{
        public XmlWriterSettings settings = new XmlWriterSettings();
        public XmlWriter writer = null;
        public string buf = "";
        public SqlShell objShell;
        public SqlCommand objCommand;
        public DataTable objDataTable;

        public menulist(string userid)
        {
            objShell = new SqlShell();
            objCommand = new SqlCommand("select * from qxdmb order by jb,px,qxdm");
            objCommand.CommandType = CommandType.Text;
            objDataTable = objShell.executeDataSet(ref objCommand).Tables[0];

            StringWriter writerstr = new StringWriter();
            settings.Indent = true;
            settings.Encoding = Encoding.GetEncoding("utf-8");
            try
            {
                writer = XmlWriter.Create(writerstr, settings);

                writer.WriteStartDocument();
                writer.WriteStartElement("DSTreeRoot");
                writer.WriteAttributeString("text", "后台管理系统-["+userid+"]");
                writer.WriteAttributeString("treeId", "0000");
                writer.WriteAttributeString("open", "true");

                 
                readqxdmb("0");

                writer.WriteEndElement();
                writer.WriteEndDocument();
            }
            finally
            {
                if (writer != null)
                    writer.Close();
            }
            buf = writerstr.ToString();
            buf = buf.Replace(@"encoding=""utf-16""", @"encoding=""utf-8""");//在使用StringWriter 作为xml输出时XML自动为“utf-16”，此处用Replace方法处理，如有更好的方法请指教！

        }

        private void readqxdmb(string sjdm)//生成XML树的方法
        {
            DataTable mytable = objDataTable.Copy();
            DataRow[] foundRows;
            foundRows = mytable.Select("sjdm='" + sjdm + "'");
            if (foundRows.Length > 0)
            {
                //写子节点
                for (int i = 0; i < foundRows.Length; i++)
                {
                    writer.WriteStartElement("DSTree");
                    writer.WriteAttributeString("text", foundRows[i]["qxsm"].ToString().Trim());
                    writer.WriteAttributeString("treeId", foundRows[i]["qxdm"].ToString().Trim());
                    writer.WriteAttributeString("open", "false");
                    //处理下级节点
                    readqxdmb((string)foundRows[i]["qxdm"]);
                    writer.WriteEndElement();
                }
            }
            mytable.Dispose();
        }

    }
}

/*menulist 结束*/