void ClearData()
 {
     ID_RESERVATION.Clear();
     AMOUNT.Clear();
     DATE_RESERVATION.Clear();
     MODEL_NAME.Clear();
     RENTAL_DAYS.Clear();
 }
        private void ID_RESERVATION_VERIFY(object sender, EventArgs e)
        {
            DataTable dt = new DataTable();

            dt = resadd.VERIFY_ID_RESERVATION(ID_RESERVATION.Text);
            if (dt.Rows.Count > 0)
            {
                MessageBox.Show("This ID Already Exist in the Database!");
                ID_RESERVATION.Focus();
                ID_RESERVATION.SelectionStart  = 0;
                ID_RESERVATION.SelectionLength = ID_RESERVATION.TextLength;
            }
        }