private void loadThongTinSanPham()
{
txtSoLuongXuat.Text = "0";
dgvDanhSachSanPham.Rows.Clear();
chiTietHoaDon = hoadonController.GetChiTietHoaDon_Show(int.Parse(txtMaHoaDon.Text));
txtSoLuongConLai.Text = (int.Parse(chiTietHoaDon.Rows[cbbTenSanPham.SelectedIndex]["soluongsanpham"].ToString()) - int.Parse(chiTietHoaDon.Rows[cbbTenSanPham.SelectedIndex]["soluongsanphamdaxuat"].ToString())).ToString();
}