0

我有这些模型：

public class Product
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }
    [Required]
    [Display(Name = "Ürün Adı")]
    public string Name { get; set; }
    [Required]
    [Display(Name = "Açıklama")]
    public string Description { get; set; }
    [Required]
    [Display(Name = "Fiyat")]
    public decimal Price { get; set; }
    [Required]
    [Display(Name = "İndirim")]
    public decimal Discount { get; set; }
    [Required]
    [Display(Name = "İndirim Geçerli Mi?")]
    public bool IsDiscountActive { get; set; }
    [Required]
    [Display(Name="Ürün Var Mı?")]
    public bool IsAvailable { get; set; }
    [Required]
    [Display(Name="Kategori")]
    public Category Category { get; set; }
    [Display(Name="Resim")]
    public Image Image { get; set; }
    [Required]
    public DateTime CreatedOn { get; set; }
    public DateTime ChangedOn { get; set; }
    [Required]
    public UserProfile CreatedBy { get; set; }
    public UserProfile ChangedBy { get; set; }

    public IEnumerable<SelectListItem> Categories
    {
        get
        {
            return new OnlineShoppingContext().Categories.OrderBy(c=>c.Name).ToList()
            .Select(e => new SelectListItem { Text = e.Name, Value = e.Id.ToString() });
        }
    }
}


[Table("Category")]
public class Category
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }
    [Required]
    [Display(Name = "Kategori Adı")]
    public string Name { get; set; }
    [Display(Name = "Açıklama")]
    public string Description { get; set; }
    [Display(Name = "Resim")]
    public Image Image { get; set; }
    [DatabaseGenerated(DatabaseGeneratedOption.Computed)]
    public DateTime CreatedOn { get; set; }
    public DateTime ChangedOn { get; set; }
    public UserProfile CreatedBy { get; set; }
    public UserProfile ChangedBy { get; set; }
    public List<Product> Products { get; set; }
}

我的类别控制器

 [Authorize(Roles = "Admin")]
public class CategoryController : Controller
{
    private OnlineShoppingContext db = new OnlineShoppingContext();

    //
    // GET: /Category/

    public ActionResult Index()
    {
        return View(db.Categories.ToList());
    }

    //
    // GET: /Category/Details/5

    public ActionResult Details(int id = 0)
    {
        Category category = db.Categories.Find(id);
        if (category == null)
        {
            return HttpNotFound();
        }
        return View(category);
    }

    //
    // GET: /Category/Create

    public ActionResult Create()
    {
        return View();
    }

    //
    // POST: /Category/Create

    [HttpPost]
    public ActionResult Create(Category category, HttpPostedFileBase file)
    {
        if (ModelState.IsValid)
        {
            if (file != null)
            {
                string pic = Guid.NewGuid().ToString();
                string path = Path.Combine(Server.MapPath("~/Content/images/"), pic + Path.GetExtension(file.FileName));
                file.SaveAs(path);
                Image i = new Image();
                i.Path = path;
                i.CreatedBy = db.UserProfiles.Where(u => u.UserId == WebSecurity.CurrentUserId).FirstOrDefault();
                category.Image = i;
            }
            category.CreatedBy = db.UserProfiles.Where(u => u.UserId == WebSecurity.CurrentUserId).FirstOrDefault();
            db.Categories.Add(category);
            db.SaveChanges();
            return RedirectToAction("Index");
        }

        return View(category);
    }

    //
    // GET: /Category/Edit/5

    public ActionResult Edit(int id = 0)
    {
        Category category = db.Categories.Find(id);
        if (category == null)
        {
            return HttpNotFound();
        }
        return View(category);
    }

    //
    // POST: /Category/Edit/5

    [HttpPost]
    public ActionResult Edit(Category category)
    {
        if (ModelState.IsValid)
        {
            db.Entry(category).State = EntityState.Modified;
            db.SaveChanges();
            return RedirectToAction("Index");
        }
        return View(category);
    }

    //
    // GET: /Category/Delete/5

    public ActionResult Delete(int id = 0)
    {
        Category category = db.Categories.Find(id);
        if (category == null)
        {
            return HttpNotFound();
        }
        return View(category);
    }

    //
    // POST: /Category/Delete/5

    [HttpPost, ActionName("Delete")]
    public ActionResult DeleteConfirmed(int id)
    {
        Category category = db.Categories.Find(id);
        db.Categories.Remove(category);
        db.SaveChanges();
        return RedirectToAction("Index");
    }

    protected override void Dispose(bool disposing)
    {
        db.Dispose();
        base.Dispose(disposing);
    }
}

创建.cshtml

@model OnlineShopping.Models.Product

@{
    var db = new OnlineShopping.Models.OnlineShoppingContext();
    ViewBag.Title = "Create";
}

<h2>Create</h2>

@using (Html.BeginForm("Create", "Product", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
    @Html.ValidationSummary(true)

    <fieldset>
        <legend>Product</legend>

        <div class="editor-label">
            @Html.LabelFor(model => model.Category)
        </div>
        <div class="editor-field"> 
           // Error Model is null
            @Html.DropDownListFor(model => model.Category, new SelectList(Model.Categories, "Value", "Text"))
            @Html.ValidationMessageFor(model => model.Category)
        </div>
        <div class="editor-label">
            @Html.LabelFor(model => model.Name)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Name)
            @Html.ValidationMessageFor(model => model.Name)
        </div>
        <div class="editor-label">
            @Html.LabelFor(model => model.Price)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Price)
            @Html.ValidationMessageFor(model => model.Price)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.Discount)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Discount)
            @Html.ValidationMessageFor(model => model.Discount)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.IsDiscountActive)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.IsDiscountActive)
            @Html.ValidationMessageFor(model => model.IsDiscountActive)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.IsAvailable)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.IsAvailable)
            @Html.ValidationMessageFor(model => model.IsAvailable)
        </div>
         <div class="editor-field">
            <input type="file" name="file" id="file" />
        </div>
        <p>
            <input type="submit" value="@Translations.Common.Create" />
        </p>
    </fieldset>
}

<div>
    @Html.ActionLink(Translations.Common.BackToList, "Index")
</div>

@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

在 create.cshtml 页面上我得到了这个错误

异常详细信息：System.NullReferenceException：对象引用未设置为对象的实例。第 19 行： 第 20 行： 第 21 行：@Html.DropDownListFor(model => model.Category, new SelectList(Model.Categories, "Value", "Text")) 第 22 行：@Html.ValidationMessageFor(model => model.类别）第 23 行：

4

2 回答 2

0

在 GET 你Model是空的，所以Model.Categories崩溃。尝试以下操作：

//
// GET: /Category/Create
public ActionResult Create()
{
    var model = new OnlineShopping.Models.Product();
    return View(model);
}
于 2013-10-28T08:34:31.530 回答
0

您的创建视图希望您传入一个模型，然后在您的视图中，它将查找模型的值来为您生成下拉列表。由于您尚未传入模型，因此您会得到该对象空引用异常。

此外，当您传入模型时，请确保它包含填充下拉列表所需的所有数据。

于 2013-10-28T08:39:42.463 回答