private void button1_Click(object sender, EventArgs e)
{
string ma = txtTenNhanVien.Text;
string tu = txtTu.Text;
string den = txtDen.Text;
Bang1.DataSource = bus.ThongKeDLSoLanNhanVienDiTour(tu, den, ma);
DataTable d = bus.ThongKeSoLanNhanVienDiTour(tu, den, ma);
if (Bang1.RowCount > 1)
{
txtSoLan.Text = d.Rows[0]["TONGSO"].ToString();
}
}