尽管较早初始化它，但视图中的空模型

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。

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");
        }
    }
}

CartMenager.cs

namespace SynergieBooksShop.Infrastructure
{
    public class CartMenager
    {
        private ProductRepo _productRepo;
        private OrderRepo _orderRepo;
        private CartPositionRepo _cartRepo;
        private ISessionMenager session;
        public CartMenager(ISessionMenager session, ProductRepo _productRepo, OrderRepo _orderRepo, CartPositionRepo _cartRepo)
        {
            this.session = session;
            this._productRepo = _productRepo;
            this._orderRepo = _orderRepo;
            this._cartRepo = _cartRepo;
        }

        public List<CartPosition> TakeCart()
        {
            List<CartPosition> cart;

            if (session.Get<List<CartPosition>>(Consts.CartSessionKey)==null)
            {
                cart = new List<CartPosition>();
            }
            else
            {
                cart = session.Get<List<CartPosition>>(Consts.CartSessionKey) as List<CartPosition>;
            }
            return cart;
        }

        public void AddToCart(int productId)
        {
            var cart = TakeCart();
            var cartPosition = cart.Find(k => k.Product.ProductId == productId);
            //var cartPositio1 = _cartRepo.GetOne(productId);

            if (cartPosition != null) 
                cartPosition.Quantity++;
            else
            {
                var productToAdd = _productRepo.GetAll().Where(p => p.ProductId == productId).SingleOrDefault();

                if (productToAdd != null)
                {
                    var newCartPosition = new CartPosition()
                    {
                        Product = productToAdd,
                        Quantity = 1,
                        Value = productToAdd.ProductPrice
                    };
                    cart.Add(newCartPosition);

                }
            }
            session.Set(Consts.CartSessionKey, cart);
        }
...

通过设置断点，我看到 CartController 与其他对象一起创建了 CartViewModel cartVM 对象，那么为什么视图将其视为 null 呢？ 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);