private void HienThi()
{
txtMaHDX.Text = ma;
txtMaHDX.Enabled = false;
dgvThanhToan.DataSource = Bus.ThanhToan("SELECT HoaDonXuat.MaKH,TenKH,MaHDX, SUM(ThanhTien) AS TongTien FROM dbo.HoaDonXuat INNER JOIN dbo.ChiTietHoaDonXuat ON ChiTietHoaDonXuat.MaHDX = HoaDonXuat.MaHoaDon INNER JOIN dbo.KhachHang ON KhachHang.MaKH = HoaDonXuat.MaKH WHERE MaHDX = '" + txtMaHDX.Text + "' GROUP BY HoaDonXuat.MaKH, TenKH, MaHDX");
}