use Html.DropDownListFor() w/o using Model

Question

I'm passing a Model into my view (.net mvc 3) that can't contain the information that I want to use to populate my drop down list.

I've never used Html.DropDownListFor() but have always just used Html.DropDownList(). I want to add another tool to my bag of tricks though and so want to try and incorporate Html.DropDownListFor().

Is it possible to use this helper with Key/Value pair set in a ViewBag variable?

Please advise, any code samples would be greatly appreciated (both front end (razor) and back end (on controller)).

TIA

Have you defined a custom display (editorfor, etc) for the datatype you want to use to populate the dropdown? — Maess
I'm confused - why can't you pass the information required to build the drop down list into the view as part of your model? If you don't have the information to build it, editorfor/dropdownfor etc aren't going to help you at all — geoffreys

Darin Dimitrov Darin Dimitrov · Accepted Answer · 2011-12-06T06:58:07

Is it possible to use this helper with Key/Value pair set in a ViewBag variable?

Absolutely not. If you want to use strongly typed helpers such as Html.DropDownListFor you need a view model. And since I always recommend using a view model, here's an example:

public class MyViewModel
{
    public string SelectedId { get; set; }
    public IEnumerable<SelectListItem> Items { get; set; }
}

As you can see in this sample view model, for each dropdown you need 2 properties: a scalar property that will hold the selected value and a collection of SelectListItem that will hold the options where each option consists of a value and text.

Then it's the controller's responsibility to initialize this view model and pass it to the view:

public ActionResult Index()
{
    var model = new MyViewModel();
    // normally those values will be dynamic. They will be mapped 
    // to the view model
    model.Items = new[]
    {
        new SelectListItem { Value = "1", Text = "item 1" },
        new SelectListItem { Value = "2", Text = "item 2" },
        new SelectListItem { Value = "3", Text = "item 3" },
    };
    return View(model);
}

and then you will have a corresponding strongly typed view to this view model in which you will be able to use the strongly typed version of the helpers:

@model MyViewModel
@Html.DropDownListFor(x => x.SelectedId, Model.Items)

The following sentence from your question deserves some attention:

I'm passing a Model into my view (.net mvc 3) that can't contain the information that I want to use to populate my drop down list.

You should not be passing a model to a view. You should be passing a view model. A view model is a class that you specifically define for each view. It will contain the necessary information that this view will require. So a single view model could be composed from multiple models simply because such are the requirements of your view.

use Html.DropDownListFor() w/o using Model

1 Answers