private void AddHD()
        {
            HoaDon hd = new HoaDon();

            hd.MaKH         = int.Parse(cbMaKHang.Text);
            hd.MaNV         = int.Parse(cbMaNVien.Text);
            hd.NgayDatHang  = dtpNgayDatHang.Value;
            hd.NgayGiaoHang = dtpNgayGiaoHang.Value;

            ChiTietHD cthd = new ChiTietHD();

            cthd.MaSP      = int.Parse(cbMaSPham.Text);
            cthd.GiaBan    = decimal.Parse(txtGiaBan.Text);
            cthd.SoLuong   = int.Parse(txtSoLuong.Text);
            cthd.GiamGia   = double.Parse(txtGiamGia.Text);
            cthd.ThanhTien = decimal.Parse(txtThanhTien.Text);

            hdBUS.AddHDBUS(hd, cthd);
        }