如何使用带有实体框架的 ASP.NET MVC 在详细信息视图中显示类别名称

Question

ItemCategory 类：

   public class ItemCategory
   {
        [Key]
        public int CategoryId { get; set; }
        [Required]
        [Display(Name ="Category Name")]
        public string CategoryName { get; set; }
        public virtual ICollection<Item> Items { get; set; }
    }

Item 类如下：

   public class Item
   {
        [Key]
        public int ItemId { get; set; }
        [Required]
        [Display(Name = "Item Name")]
        public string ItemName { get; set; }
        [DataType(DataType.Currency)]
        public decimal Price { get; set; }
        [DataType(DataType.Text)]
        [Display(Name ="Category Code")]
        public int CategoryId { get; set; }

        public ItemCategory ItemCategory { get; set; }
        [NotMapped]
        public string CategoryName { get; set; }
   }

这是项目控制器的代码：

   // GET: Items/Details/5
   public async Task<ActionResult> Details(int? id)
   {
      if (id == null)
      {
         return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
      }

      var items =  db.Items.Include(i => i.ItemCategory);

      if (items == null)
      {
          return HttpNotFound();
      }

      //var thisItem = db.Items.FirstOrDefault(item => item.ItemId == id);
      return View(await db.Items.FindAsync(id));
}

查看代码如下：

@model ContactManager.Models.Item
@{
    ViewBag.Title = "Details";
}
<h2>Details</h2>
<div>
    <h4>Item</h4>
    <hr />
    <dl class="dl-horizontal">
        <dt>
            @Html.DisplayNameFor(model => model.ItemCategory.CategoryName)
        </dt>
        <dd>
            @Html.DisplayFor(model => model.ItemCategory.CategoryName)
        </dd>
        <dt>
            @Html.DisplayNameFor(model => model.ItemCode)
        </dt>
        <dd>
            @Html.DisplayFor(model => model.ItemCode)
        </dd>
        <dt>
            @Html.DisplayNameFor(model => model.ItemName)
        </dt>
        <dd>
            @Html.DisplayFor(model => model.ItemName)
        </dd>
        <dt>
            @Html.DisplayNameFor(model => model.Price)
        </dt>
        <dd>
            @Html.DisplayFor(model => model.Price)
        </dd>
        <dt>
            @Html.DisplayNameFor(model => model.BarCode)
        </dt>
        <dd>
            @Html.DisplayFor(model => model.BarCode)
        </dd>
    </dl>
</div>
<p>
    @Html.ActionLink("Edit", "Edit", new { id = Model.ItemId }) |
    @Html.ActionLink("Back to List", "Index")
</p>

我是 ASP.NET MVC 和实体框架的新手。当我执行代码时，视图不会在此视图中显示类别名称，我真的很想知道如何在此视图中获取类别名称....谢谢

Answer 1

ItemCategory.CategoryName 引用为空。更改您的 Item 模型。它会起作用的。

  public class Item
    {
        public Item() // Note this
        {
            ItemCategory = new ItemCategory();
        }
        [Key]
        public int ItemId { get; set; }
        [Required]
        [Display(Name = "Item Name")]
        public string ItemName { get; set; }
        [DataType(DataType.Currency)]
        public decimal Price { get; set; }
        [DataType(DataType.Text)]
        [Display(Name = "Category Code")]
        public int CategoryId { get; set; }

        public ItemCategory ItemCategory { get; set; }
        [NotMapped]
        public string CategoryName { get; set; }
    }