private void EditStaff(object sender, DataGridViewCellEventArgs e)
        {
            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();
            string gender = selectedRow.Cells[Constant.OPERATION_INDEX_THREE].Value == null ? string.Empty : selectedRow.Cells[Constant.OPERATION_INDEX_THREE].Value.ToString();
            DateTime joinDate = (DateTime)selectedRow.Cells[Constant.OPERATION_INDEX_FOUR].Value;
            string position = selectedRow.Cells[Constant.OPERATION_INDEX_FIVE].Value == null ? string.Empty : selectedRow.Cells[Constant.OPERATION_INDEX_FIVE].Value.ToString();
            string email = selectedRow.Cells[Constant.OPERATION_INDEX_SIX].Value == null ? string.Empty : selectedRow.Cells[Constant.OPERATION_INDEX_SIX].Value.ToString();
            string contact = selectedRow.Cells[Constant.OPERATION_INDEX_SEVEN].Value == null ? string.Empty : selectedRow.Cells[Constant.OPERATION_INDEX_SEVEN].Value.ToString();
            DateTime passwordExpireDate = (DateTime)selectedRow.Cells[Constant.OPERATION_INDEX_EIGHT].Value;
            DateTime birthDate = (DateTime)selectedRow.Cells[Constant.OPERATION_INDEX_NINE].Value;
            bool defaultPassword = (bool)selectedRow.Cells[Constant.OPERATION_INDEX_TEN].Value;
            bool blocked = (bool)selectedRow.Cells[Constant.OPERATION_INDEX_ELEVEN].Value;

            AddEditStaff frmEditStaff = new AddEditStaff(name, staffID, email, passwordExpireDate, birthDate, joinDate, gender, position, contact, defaultPassword, blocked);
            frmEditStaff.ShowDialog();
        }
 private void btnAddStaff_Click(object sender, EventArgs e)
 {
     AddEditStaff frmAddStaff = new AddEditStaff();
     frmAddStaff.ShowDialog();
     ColorAndSortStaff();
 }