private void EditStaff(object sender, DataGridViewCellEventArgs e)
        {
            try
            {
                if (e.RowIndex == -1)
                    return;
                if (dgvStaff.SelectedRows.Count == Constant.CONSTANT_ZERO)
                    return;
                DataGridViewRow selectedRow = dgvStaff.SelectedRows[Constant.CONSTANT_ZERO];

                string staffID = selectedRow.Cells[Constant.OPERATION_INDEX_ONE].Value == null ? string.Empty : selectedRow.Cells[Constant.OPERATION_INDEX_ONE].Value.ToString();
                string name = selectedRow.Cells[Constant.OPERATION_INDEX_TWO].Value == null ? string.Empty : selectedRow.Cells[Constant.OPERATION_INDEX_TWO].Value.ToString();
                DateTime renewPasswordDate = (DateTime)selectedRow.Cells[Constant.OPERATION_INDEX_SEVEN].Value;
                DateTime dateOfBirth = (DateTime)selectedRow.Cells[Constant.OPERATION_INDEX_EIGHT].Value;
                DateTime joinDate = (DateTime)selectedRow.Cells[Constant.OPERATION_INDEX_FOUR].Value;
                string gender = selectedRow.Cells[Constant.OPERATION_INDEX_THREE].Value == null ? string.Empty : selectedRow.Cells[Constant.OPERATION_INDEX_THREE].Value.ToString();
                string position = selectedRow.Cells[Constant.OPERATION_INDEX_FIVE].Value == null ? string.Empty : selectedRow.Cells[Constant.OPERATION_INDEX_FIVE].Value.ToString();
                string contact = selectedRow.Cells[Constant.OPERATION_INDEX_SIX].Value == null ? string.Empty : selectedRow.Cells[Constant.OPERATION_INDEX_SIX].Value.ToString();
                bool defaultPassword = selectedRow.Cells[Constant.OPERATION_INDEX_NINE].Value == null ? false : (bool)selectedRow.Cells[Constant.OPERATION_INDEX_NINE].Value;
                bool blocked = selectedRow.Cells[Constant.OPERATION_INDEX_TEN].Value == null ? false : (bool)selectedRow.Cells[Constant.OPERATION_INDEX_TEN].Value;

                AddEditStaff frmEditStaff = new AddEditStaff(name, staffID, renewPasswordDate, dateOfBirth, joinDate, gender, position, contact, defaultPassword, blocked);
                frmEditStaff.ShowDialog();
            }
            catch
            {
                throw;
            }
        }
 private void btnAddStaff_Click(object sender, EventArgs e)
 {
     AddEditStaff frmAddStaff = new AddEditStaff();
     frmAddStaff.ShowDialog();
 }