public static void create_xml(string sql, string top_node, string xml_filename)
    {
      String se = System.AppDomain.CurrentDomain.BaseDirectory;
        string consql = ConfigurationSettings.AppSettings["consql"].ToString();
        SqlConnection con = new SqlConnection(consql);
        con.Open();
        SqlCommand cmd = new SqlCommand(sql,con);
        System.Xml.XmlTextReader rd;
        rd = (System.Xml.XmlTextReader)cmd.ExecuteXmlReader();
        System.IO.StreamWriter w = new System.IO.StreamWriter(xml_filename, false, System.Text.Encoding.GetEncoding("gb2312"));
        w.WriteLine("<?xml version='1.0'encoding='gb2312'?>");
        w.WriteLine("<"+top_node+">");
        while (rd.IsStartElement()) 
            w.WriteLine(rd.ReadOuterXml());
            w.WriteLine("</"+top_node+">");
            w.Close();
            rd.Close();
            con.Close();
    }

 protected void Button5_Click(object sender, EventArgs e)
    {
        string xml = TextBox5.Text;
        string gen = "stundet";
        stat.create_xml("select stor_id,stor_name,stor_address from stores for xml auto",gen,Server.MapPath(""+xml+".xml"));
    }