protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            SetContentView(Resource.Layout.Checkout_layout);
            Cheeseknife.Inject(this);
            products = Ultilities.GetData <Product>("data.json");
            adapter  = new BillAdapter(products);
            rvProducts.SetLayoutManager(new LinearLayoutManager(this));
            rvProducts.SetAdapter(adapter);

            tvBillMoney.Text = products.Sum(p => p.Count * p.UnitPrice) + " vnd";
        }