Question

我在创建购物车时遇到问题。我已经创建了支持添加的整个机制，但是当我尝试使用产品读取模型时，出现错误： System.NullReferenceException：“对象引用未设置为对象的实例。” System.Web.Mvc.WebViewPage .Model.get返回null。

1. [1, 1, 1, 1, 1, 0, 0]
2. [1, 1, 1, 1, 0, 1, 0]
3. [1, 1, 1, 1, 0, 0, 1]
4. [1, 1, 1, 0, 1, 1, 0]
5. [1, 1, 1, 0, 1, 0, 1]
6. [1, 1, 1, 0, 0, 1, 1]
7. [1, 1, 0, 1, 1, 1, 0]
8. [1, 1, 0, 1, 1, 0, 1]
9. [1, 1, 0, 1, 0, 1, 1]
10. [1, 1, 0, 0, 1, 1, 1]
11. [1, 0, 1, 1, 1, 1, 0]
12. [1, 0, 1, 1, 1, 0, 1]
13. [1, 0, 1, 1, 0, 1, 1]
14. [1, 0, 1, 0, 1, 1, 1]
15. [1, 0, 0, 1, 1, 1, 1]
16. [0, 1, 1, 1, 1, 1, 0]
17. [0, 1, 1, 1, 1, 0, 1]
18. [0, 1, 1, 1, 0, 1, 1]
19. [0, 1, 1, 0, 1, 1, 1]
20. [0, 1, 0, 1, 1, 1, 1]
21. [0, 0, 1, 1, 1, 1, 1]

index.cshtml

@model SynergieBooksShop.ViewModels.CartViewModel
@using SynergieBooksShop.Infrastructure
@{
    ViewBag.Title = "Cart";
}

<h2>Index</h2>

@foreach (var cartPosition in Model.CartPositions)  <---- Here is error
{
    @cartPosition.Product.ProductTitle <br>
    @cartPosition.Quantity <br>
    @cartPosition.Value
}

<div id="cart-empty-message" @if (Model.CartPositions != null && Model.CartPositions.Count > 0) { <text>class="hidden"</text>}>
 <p>Your cart is empty</p>
</div>

</hr>
Total Price: <span id="total-price">@Model.TotalPrice</span> pln

CartViewModel.cs

namespace SynergieBooksShop.ViewModels
{
    public class CartViewModel
    {
        public List<CartPosition> CartPositions { get; set; }
        public decimal TotalPrice { get; set; }
    }
}

CartController.cs

namespace SynergieBooksShop.Controllers
{
    public class CartController : Controller
    {
        private CartMenager cartMenager;
        private ISessionMenager sessionMenager { get; set; }
        private ProductRepo _productRepo;
        private OrderRepo _orderRepo;
        private CartPositionRepo _cartRepo;

        public CartController(){
            _productRepo = new ProductRepo();
            _orderRepo = new OrderRepo();
            _cartRepo = new CartPositionRepo();
            sessionMenager = new SessionMenager();
            cartMenager = new CartMenager(sessionMenager, _productRepo, _orderRepo, _cartRepo);
        }

        // GET: Cart
        public ActionResult Index()
        {
            var cartPositions = cartMenager.TakeCart();
            var totalPrice = cartMenager.TakeCartValue();
            CartViewModel cartVM = new CartViewModel()
            {
                CartPositions = cartPositions,
                TotalPrice = totalPrice
            };

            return View();
        }

        public ActionResult AddToCart(int id)
        {
            cartMenager.AddToCart(id);
            return RedirectToAction("Index");
        }
    }
}

通过放置断点，我看到CartController与其他对象一起创建了CartViewModel cartVM对象，为什么视图将其视为null？感谢您的帮助：）

Answer 1

您没有将数据返回到视图。应该是：

return View(cartVM);

尽管模型已提前初始化，但仍为空模型

1 个答案: