private void QRdisplayForm_FormClosed(object sender, FormClosedEventArgs e)
        {
            ClassController classController = new ClassController();

            try
            {
                Console.WriteLine("trying");
                classController.InsertQRDisplayEndTime(Class.Id, DateTime.Now.ToString());
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }