private void btnRemoveShifts_Click(object sender, EventArgs e)
        {
            List <Shift> selectedShifts = GetSelectedShifts();

            if (selectedShifts.Count == 0)
            {
                MessageBox.Show("No shift is selected.");
                return;
            }

            if (Util.Confirm("Are you sure you want to delete all selected shift(s)?"))
            {
                if (_dtCtrl.DeleteShifts(selectedShifts))
                {
                    MessageBox.Show("Shift(s) deleted.");
                }
                else
                {
                    MessageBox.Show("Shift(s) could not deleted. Please try again.");
                }

                _shiftList = _dtCtrl.GetShiftListByWorkingCalendar(_workingCalendarID);
                BindShift();
            }
        }