query ข้อมูลจาก datatable ค่ะ ถ้าเราเลือกข้อมูลใน dropdownlist เราจะได้แค่ "id" กับ "description"

                    DataTable rec = new DataTable();
                    rec.Columns.AddRange(new DataColumn[] { 
                    new DataColumn("id", typeof(string)),
                    new DataColumn("price", typeof(string)),
                    new DataColumn("description", typeof(string))
                          });
            
                    XmlDocument doc = new XmlDocument();
                    doc.LoadXml(returnxml);
                    foreach (XmlNode recNode in doc.GetElementsByTagName("detail"))
                    {
                        DataRow row = rec.Rows.Add(
                        recNode["id"].InnerText,
                        recNode["price"].InnerText,
                        recNode["description"].InnerText);
                       //Response.Write("" + ": " + recNode["id"].InnerText + "<br />");  
                  
                    }

                    dropdownlist.DataSource = rec.DefaultView;
                    dropdownlist.DataValueField = rec.Columns["id"].ToString();
                    dropdownlist.DataTextField = rec.Columns["description"].ToString();
                    dropdownlist.DataBind();