เกี่ยวกับเรื่อง WMI วานผู้รู้ไขข้อข้องใจหน่อย ครับ

try
        {
            string sql = "select * from " + ddlService.SelectedValue + " ";
            ManagementObjectSearcher query = new ManagementObjectSearcher(sql);
            ManagementObjectCollection queryCollection = query.Get();
            foreach (ManagementObject mo in queryCollection)
            {
                foreach (PropertyData prop in mo.Properties)
                {
                    Literal1.Text += prop.Name + " : " + prop.Value + "<br/>";
                }
                Literal1.Text += "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++<br/>";
            }
        }
        catch
        {
            Literal1.Text = "Not found Class";
        }