private void BtnDelete_Click(object sender, EventArgs e)
{
DialogResult a = MessageBox.Show("Xóa NCC này!", "Thông báo!", MessageBoxButtons.OKCancel, MessageBoxIcon.Question);
if (a == DialogResult.OK)
{
db.XoaNCC(Convert.ToInt32(txtMaNCC.Text));
dgvNCC.DataSource = db.NCCtable();
}
}