Question

I have two classes Item and Category. Items may belong to a single category. In the implementation I am using NHibernate and Item has a Category property (of type Category). Both classes are entities.

I wonder how to make it possible in a view for editing an item to be able to choose a category for example from a list or drop-down list. There are HTML helpers like Html.DropDownListFor but I don’t know how to make it work when I need to select an object (NHibernate doesn’t make CategoryId for Item accessible). Could anybody help me with the problem?

Thanks in advance
Lukasz

Answer 1

You should be using view models in all cases. So no matter how your NHibernate models look like you are trying to display a drop down list in the view. So as always you start by defining a view model that will hold the necessary information to be used by this view:

public class CategoryViewModel
{
    public int SelectedItemId { get; set; }
    public IEnumerable<SelectListItem> Items { get; set; }
}

and then you would have a controller action which will fetch the model from a repository and map it to this view model:

public ActionResult Index()
{
    Category category = ...
    // Example using AutoMapper
    CategoryViewModel viewModel = Mapper.Map<Category, CategoryViewModel>(category);
    return View(viewModel);
}

and in the view simply:

@Html.DropDownListFor(
    x => x.SelectedItemId,
    new SelectList(Model.Items, "Value", "Text")
)

If you don’t use view models you will be struggling to adapt your existing models to situations for which they weren’t meant to be.