Best way to populate SelectList for ViewModel on GET/POST

Question

I have the following ViewModel:

public class EditViewModel
{
    public int FooType { get; set; }
    public IEnumerable<SelectListItem> FooTypes { get; set; }
}

I originally populated it in my Edit action like so:

public ActionResult Edit(int id)
{
    EditViewModel model = new EditViewModel();
    model.FooTypes = new SelectList(repository.GetFooTypes(), "Id", "Value");

    return View(model);
}

When I created the action to POST the values I had to repeat the same code:

public ActionResult Edit(int id, EditViewModel model)
{
    if( !ModelState.IsValid )
    {
        model.FooTypes = new SelectList(repository.GetFooTypes(), "Id", "Value");

        return View(model);
    }

    return RedirectToAction("Index");
}

I don't like having this code in two separate locations. Is there any common practice for refactoring this into a single spot so I dont need to repeat this code?

Answer 1

Given that c# is an object oriented language, there are plenty of options available.

The simplest would be to just wrap it in a method within the controller:

private SelectList GetFooTypesList()
{
    return new SelectList(repository.GetFooTypes(), "Id", "Value);
}

and call it when setting up your model

or if you're using it in multiple classes you could create a helper method in another class that accepts the repository or an IEnumerable as a parameter.

If you want to get really advanced, you could use a ModelFactory to create the FooType model for you, with a prepopulated FooType property so the controller doesn't need to worry about it at all.

There's plenty of options, you just need to pick the one that's best for you.

My personal preference is the simple helper method in the controller.