asp.net - ViewModel 在 Add [HttpPost] 方法上为空

Question

我有以下内容ViewModel：

public class CategoryViewModel
{
    public Category Category { get; set; }
    public IList<Category> Categories { get; set; }
    public IList<Product> Products { get; set; }

    public IEnumerable<SelectListItem> CategorySelectItems
    {
        get { var ret = new List<SelectListItem>();
        if(Categories==null)
            return ret;

            ret.AddRange(Categories.Where(x => (Category == null || x.Id != 
                        Category.Id)).Select(category => new SelectListItem 
                                     { Text = category.Name, Value = 
                                        category.Id.ToString()}));
            return ret;
        }
    }

    public CategoryViewModel(){}
}

以下是控制器：

namespace mysite.com.Controllers{
    public class CategoryController : Controller{
        private IRepository<Category> _repository;
        private IRepository<Product> _productRepo;
        private CategoryViewModel _categoryViewModel;

        public CategoryController(){
            _repository = new CategoryRepository();
            _productRepo = new ProductRepository();
        }

        [HttpGet]
        public ActionResult Index(){
           return View(new CategoryViewModel{Categories=_repository.GetAll()});
        }

        [HttpGet]
        public ActionResult Add(){
            return View(new CategoryViewModel{
           Category = new Category(), Categories= _repository.GetAll()});
        }

        [HttpPost]
        public ActionResult Add(CategoryViewModel category){
            if (ModelState.IsValid){
                _repository.Save(category.Category);
                return RedirectToAction("Index");
            }
            return View(category);
        }
    }
}

这是我认为的代码：

@model mysite.com.ViewModels.CategoryViewModel

@using (Html.BeginForm("Add", "Category", FormMethod.Post))
{
    @Html.ValidationSummary(true)
    <fieldset>
        <legend>Add Category</legend>
        @Html.HiddenFor(x => x.Category.Id)
        <div class="editor-label">
            @Html.LabelFor(x => x.Category.Name)
        </div>
        <div class="editor-field">
            @Html.EditorFor(x => x.Category.Name)
            @Html.ValidationMessageFor(x => x.Category.Name)
        </div>
        <div class="editor-label">
            @Html.LabelFor(x => x.Category.ParentCategory)
        </div>
        <div class="editor-field">
            @Html.DropDownList("ParentCategory", 
                     Model.CategorySelectItems,"--select parent category--")
            @Html.ValidationMessageFor(x => x.Category.Name)
        </div>
        <p>
            <input type="submit" value="Save" />
        </p>
    </fieldset>
}
<div>
    @Html.ActionLink("Back to List", "Index")
</div>

但是在我的控制器的[HttpPost] Add方法中，category对象（类型CategoryViewModel）是空的:(

我做错了什么？

Answer 1

您的模型不可反序列化。你的模型只能反序列化原始属性和原始属性的集合，没有太多帮助，而且这些帮助通常是不值得的。

您的模型应如下所示：

public class CategoryAddModel
{
    //these values are used to populate the view, but will not deserialize
    public IList<Category> AvailableCategories { get; set; }

    //these values are deserializable
    public int CategoryId {get;set;}
    public string CategoryName {get;set;}
    public int ParentCategory {get;set;}
}

public class CategoryIndexModel
{
    public IList<Category> Categories { get; set; }
}

您的Add.cshtml视图看起来像这样：

@model mysite.com.ViewModels.CategoryAddModel

@using (Html.BeginForm())
{
    @Html.ValidationSummary(true)
    <fieldset>
        <legend>Add Category</legend>
        @Html.HiddenFor(x => x.CategoryId)
        <div class="editor-label">
            @Html.LabelFor(x => x.CategoryName)
        </div>
        <div class="editor-field">
            @Html.EditorFor(x => x.CategoryName)
            @Html.ValidationMessageFor(x => x.CategoryName)
        </div>
        <div class="editor-label">
            @Html.LabelFor(x => x.Category.ParentCategory)
        </div>
        <div class="editor-field">
            @Html.DropDownList("ParentCategory", 
                new SelectList(Model.AvailableCategories, "Id", "Name"),
                "--select parent category--")
            @Html.ValidationMessageFor(x => x.ParentCategory)
        </div>
        <p>
            <input type="submit" value="Save" />
        </p>
    </fieldset>
}
<div>
    @Html.ActionLink("Back to List", "Index")
</div>

您的Index.cshtml视图应如下所示：

@model mysite.com.ViewModels.CategoryIndexModel
@Html.ActionLink("Add Category", "Add")
<ul>
@foreach(var item in Model.Categories)
{
    <li> @{ // List your categories, hyperlinks to editing pages } </li>
}
</ul>

你CategoryController.cs应该是这样的：

namespace mysite.com.Controllers{
    public class CategoryController : Controller
    {
        private IRepository<Category> _repository = new CategoryRepository();
        private IRepository<Product> _productRepo = new ProductRepository();

        public ActionResult Index()
        {
            var model = new CategoryIndexModel
            {
                Categories=_repository.GetAll()
            };

            return View(model);
        }

        public ActionResult Add()
        {
            var model = new CategoryAddModel()
            {
                AvailableCategories = _repository.GetAll()
            };
            return View(model);
        }

        [HttpPost]
        public ActionResult Add(CategoryAddModel model){
            if (ModelState.IsValid)
            {
                //TODO: (varies based on your repository model)
                //create a Category object from the model and persist it here.

                return RedirectToAction("Index");
            }
            //the complex collection does not return with the model; repopulate it here.
            model.AvailableCategories = _repository.GetAll()
            return View(model);
        }
    }
}

这应该让您进入您正在寻找的一般区域。

Answer 2

我认为您返回值太快了：

if(Categories==null)
        **return ret;**

        ret.AddRange(Categories.Where(x => (Category == null || x.Id != 
                    Category.Id)).Select(category => new SelectListItem 
                                 { Text = category.Name, Value = 
                                    category.Id.ToString()}));
        return ret;
    }