private void frmXuatHoaDon_Load(object sender, EventArgs e)
        {
            XuatHoaDon report = new XuatHoaDon();

            report.SetDataSource(HoaDonCtr.XuatHoaDon(mahd));
            crtpvXuatHoaDon.ReportSource = report;
        }
 private void btnLapHoaDonMoi_Click(object sender, EventArgs e)
 {
     i                       = 0;
     Tien                    = 0;
     txtTongtien.Text        = "0";
     btnGhiHoaDon.Enabled    = true;
     btnLapHoaDonMoi.Enabled = false;
     btnThemSach.Enabled     = false;
     txtMaHD.Enabled         = false;
     txtMaHD.Text            = HoaDonCtr.GetIDHoaDon();
     txtMaKH.Enabled         = true;
     txtMaNV.Text            = manv;
     loadCombox();
 }