private void button1_Click(object sender, EventArgs e) { if (cbbMatour.Text != null) { //string ma = cbbMatour.Text; ma = a[vt]; cbbMaDoan.Items.Add("Tất cả"); for (int i = 0; i < bus1.getMaDoanDeThongKeChiPhi(ma, dateTimePicker1.Text, dateTimePicker2.Text).Rows.Count; i++) { cbbMaDoan.Items.Add(bus1.getMaDoanDeThongKeChiPhi(ma, dateTimePicker1.Text, dateTimePicker2.Text).Rows[i]["MADOAN"].ToString()); } dataGridView1.DataSource = bus1.ThongKeChiPhiTatCaDoanTheoTour(ma, dateTimePicker1.Text, dateTimePicker2.Text); } else { MessageBox.Show("Ko thể thống kê"); } }