private void button1_Click(object sender, EventArgs e) { switch (typeSearch) { case 1: { dataGridView4.DataSource = Sach_BUS.TimTheoTheLoai(int.Parse(textBox1.Text)); break; } case 2: { dataGridView4.DataSource = Sach_BUS.TimTheoTacGia(textBox1.Text); break; } case 3: { dataGridView4.DataSource = Sach_BUS.TimTheoTenSach(textBox1.Text); break; } case 4: { dataGridView4.DataSource = Sach_BUS.TimTheoMaSach(int.Parse(textBox1.Text)); break; } } }