C# 外键属性赢得'；设置不正确

我之前发布了一篇类似代码的帖子，并更新了模型，使用了一个helper类而不是ViewBag。在数据库更新之前，它似乎很有魅力

这些是我的模型课

[Table("Store")]
    public class Store
    {
        [Key]
        public int StoreId { get; set; }

        public string Name { get; set; }

        public string Address { get; set; }
    }

当我的代码指向db.Purchases.Add（purchase）时，purchase对象的Store属性设置为null。然而，StoreId似乎非常好。我不明白为什么Store对象不会随着StoreId属性而改变，因为我已经用[ForeignKey（“StoreId”）]对它进行了注释。我在哪里搞砸了StoreId和Store之间的连接

更新#2

@model IEnumerable
@{
ViewBag.Title=“Index”；
}
指数

@ActionLink（“新建”、“创建”）

@DisplayNameFor（model=>model.Store.Name）
@DisplayNameFor（model=>model.Type）
@DisplayNameFor（model=>model.Price）
@DisplayNameFor（model=>model.Date）
@foreach（模型中的var项目）{
@DisplayFor（modelItem=>（item.Store.Name））
@DisplayFor（modelItem=>item.Type）
@DisplayFor（modelItem=>item.Price）
@DisplayFor（modelItem=>item.Date）
@ActionLink（“编辑”，“编辑”，新的{id=item.id}）|
@ActionLink（“详细信息”，“详细信息”，新的{id=item.id}）|
@ActionLink（“删除”，“删除”，新的{id=item.id}）
}

更新#3

---

我假设您看不到purchase.Store的任何值，这是因为模型绑定器仅绑定您在中指定的StoreId（当请求从浏览器发送到Web服务器时）

@Html.DropDownListFor(model => model.Purchase.StoreId, new SelectList(Model.Stores.Select( x => new { StoreId = x.StoreId, DisplayName = x.Name.ToString() + " - " + x.Address.ToString()}), "StoreId", "DisplayName"), new { @class = "form-control" })

purchase.Store的填充属于EF。执行此操作时，EF将加载该存储

dbContext.Purchases.Include(x => x.Store).FirstOrDefault(x => x.ID == 1234);

更新：

如果要在后期操作中使用存储对象

    // POST: Purchases/Create
    // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
    // more details see https://go.microsoft.com/fwlink/?LinkId=317598.
    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Create(Purchase purchase)
    {
        if (ModelState.IsValid)
        {
            db.Purchases.Add(purchase);
            db.SaveChanges();
            purchase = dbContext.Purchases.Include(x => x.Store).FirstOrDefault(x => x.ID == purchase.ID); // Not sure why you need Store information at this step.
            return RedirectToAction("Index");
        }

        return View(purchase);
    }

---

我必须在哪个类中添加此代码？在PurchaseDBContext中？在您的示例中，有两个操作GET和POST。您遇到了哪一个问题？post-one，在post方法中添加代码似乎无法解决问题。我已将代码添加到您的post操作中。但是，我仍然不明白为什么在重定向到索引页时需要存储数据。存储仍然为空，因此在索引页中没有显示存储名称。

        // GET: Purchases/Create
        public ActionResult Create()
        {
            var purchaseHelper = new PurchaseCreateHelper()
            {
                Stores = db.Stores.ToList(),
                Purchase = new Purchase()
            };

            return View(purchaseHelper);
        }

        // POST: Purchases/Create
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
        // more details see https://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Create(Purchase purchase)
        {
            if (ModelState.IsValid)
            {
                db.Purchases.Add(purchase);
                db.SaveChanges();
                return RedirectToAction("Index");
            }

            return View(purchase);
        }

        // GET: Purchases
        public ActionResult Index()
        {
            return View(db.Purchases.ToList());
        }

@model IEnumerable<BookKeeper.Models.Purchase>

@{
    ViewBag.Title = "Index";
}

<h2>Index</h2>

<p>
    @Html.ActionLink("Create New", "Create")
</p>

<table class="table">
    <tr>
        <th>
            @Html.DisplayNameFor(model => model.Store.Name)
        </th>
        <th>
            @Html.DisplayNameFor(model => model.Type)
        </th>
        <th>
            @Html.DisplayNameFor(model => model.Price)
        </th>
        <th>
            @Html.DisplayNameFor(model => model.Date)
        </th>
        <th></th>
    </tr>

@foreach (var item in Model) {
<tr>
    <td>
        @Html.DisplayFor(modelItem => (item.Store.Name))
    </td>
    <td>
        @Html.DisplayFor(modelItem => item.Type)
    </td>
    <td>
        @Html.DisplayFor(modelItem => item.Price)
    </td>
    <td>
        @Html.DisplayFor(modelItem => item.Date)
    </td>
    <td>
        @Html.ActionLink("Edit", "Edit", new { id = item.Id }) |
        @Html.ActionLink("Details", "Details", new { id = item.Id }) |
        @Html.ActionLink("Delete", "Delete", new { id = item.Id })
    </td>
</tr>
}

</table>

@Html.DropDownListFor(model => model.Purchase.StoreId, new SelectList(Model.Stores.Select( x => new { StoreId = x.StoreId, DisplayName = x.Name.ToString() + " - " + x.Address.ToString()}), "StoreId", "DisplayName"), new { @class = "form-control" })

dbContext.Purchases.Include(x => x.Store).FirstOrDefault(x => x.ID == 1234);

    // POST: Purchases/Create
    // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
    // more details see https://go.microsoft.com/fwlink/?LinkId=317598.
    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Create(Purchase purchase)
    {
        if (ModelState.IsValid)
        {
            db.Purchases.Add(purchase);
            db.SaveChanges();
            purchase = dbContext.Purchases.Include(x => x.Store).FirstOrDefault(x => x.ID == purchase.ID); // Not sure why you need Store information at this step.
            return RedirectToAction("Index");
        }

        return View(purchase);
    }