asp.net-mvc - 为级联子列表构建一个空的 MVC DropdownListFor

Question

我想构建一个空的 Dropdownlistfor 来接收先前 Dropdownlisfor 选择的结果:

实际 View :

    <div id="makes">
        @Html.DropDownListFor(m => m.Make_Id, Model.MakeList, HeelpResources.DropdownlistMakeFirstRecord)
    </div>
    <div id="models">
        @Html.DropDownListFor(m => m.Model_Id, Model.ModelList, HeelpResources.DropdownlistModelFirstRecord)
    </div>        

实际的 Controller (为了工作，我必须构建一个空的 SelectedList，但必须这样做似乎很奇怪):

   public virtual ActionResult Create()
    {
        // Build the Dropdownlist for the Makes
        var makesDto = _makeService.ListAllMakes();
        var makesViewModel = Mapper.Map<IList<MakeDto>, IList<MakeViewModel>>(makesDto);

        // Build the Dropdownlist for the Models
        var makeId = -1;
        var modelsDto = _modelService.ListModelByMake(makeId);
        var modelsViewModel = Mapper.Map<IList<ModelDto>, IList<ModelViewModel>>(modelsDto);

        // Build the ViewModel to return to the View
        CreateAdViewModel viewModel = new CreateAdViewModel();
        viewModel.MakeList = new SelectList(makesViewModel, "ID", "Name");
        viewModel.ModelList = new SelectList(modelsViewModel, "ID", "Name"); 

        return View(viewModel);
    }

有没有办法构建这样的东西: @Html.DropDownListFor(m => m.Model_Id, null)

并从 Controller 中删除//Build the Dropdownlist for the Models？

谢谢

Answer 1

找到了一个我认为最好的解决方案，因为它不需要服务调用来构建空的 dropdroplist，并且它是强类型的:

@Html.DropDownListFor(m => m.Model_Id, Enumerable.Empty<SelectListItem>(), HeelpResources.DropdownlistModelFirstRecord)