private void dgvthongke_CellClick(object sender, DataGridViewCellEventArgs e)
{
try
{
tbxten.ResetText();
tbxvoucher.ResetText();
int r = dgvthongke.CurrentCell.RowIndex;
int idbill = (int)dgvthongke.Rows[r].Cells[0].Value;
dgvdetails.DataSource = bill.BillDetails(idbill);
tbxten.Text = nhanvien.GetNameEmployeeFromBill(idbill);
tbxvoucher.Text = voucher.GetNameVoucherFromBill(idbill);
}
catch { }
}