Build an empty MVC DropdownListFor for a Cascade Sub-List

Question

I would like to build an empty Dropdownlistfor to received the results of a previous Dropdownlisfor selection:

The actual 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>        

The actual Controller (to work I had to build an empty SelectedList but it seems strange to have to do this):

   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);
    }

Is there a way to build something like this: @Html.DropDownListFor(m => m.Model_Id, null)

And remove the // Build the Dropdownlist for the Models from the controller?

Thanks

Shriek

Answer 1

Found a solution that I think is the best because it as no service call to build the dropdroplist empty and it's strongly typed:

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

Shriek

It would be good if you marked this as the answer to your own question. – Unhesitating

what is the use of "HeelpResources.DropdownlistModelFirstRecord"? – Streetcar

It's the text that you want to put in the first option like "Please Select an option...", but based in a Resource String so you can present this text based in the location's language website (French/Portuguese/English) – Shriek

Answer 2

The following is working:

@Html.DropDownListFor(m => m.Model_Id, **new SelectList(new List<string>()**));

Conglutinate

Answer 3

Personally I would do this with a bit of jQuery and an additional partial view. Your form could look like this:

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

</div>

<script type="text/javascript">
$(function(){
   $("#Make_Id").change(function(){
       $("#models").load("/Controller_Name/GetModels/" + this.val());
   }
});
</script>  

and then in your controller:

public ActionResult GetModels(int id)
{
   ViewBag.DdlModels = new SelectList(rep.GetModelsForCar(id), "Id", "Name");
   return PartialView();
}

and then just stick your drop down list in the GetModels partial view

Pantheas

And the Model dropdown gets strongly typed in the view coming the partial view? It will pass the Model_Id selected value from the dropdown to the controller inside the viewmodel? – Shriek