ViewModel objects to EF model entities conversion where?

Question

I currently have a repository based on Entity Framework v4 entities (CRUD and GET operations implemented). I'm in the process of creating the corresponding View Models for these entities. Where should I put the conversion/mapping between them? In the controller or modify the repository to perform the mapping in its methods and return back (or accept) the View Model typed objects?

Should I do this

    public ActionResult Index()
    {
        var person = new PersonRepository().Get();

        var personViewModel = new PersonViewModel();
        personViewModel.InjectFrom(person)
            .InjectFrom<CountryToLookup>(person);

        return View(personViewModel);
    }

or this

     public ActionResult Index()
        {
            var personViewModel = new PersonRepository().Get(); // returns object of type PersonViewModel

// and move this to repository
//            var personViewModel = new PersonViewModel();
//            personViewModel.InjectFrom(person)
//               .InjectFrom<CountryToLookup>(person);

            return View(personViewModel);
        }

since you're using valueinjecter I strongly recommend you to look at the source code of the live demo from here http://awesome.codeplex.com/, look at the Cruder (Controller) and implementations of IBuilder — Omu, Jan 19 '11 at 18:15

score 3 · Answer 1 · answered Jan 18 '11 at 17:29

I would extract it out into a private method on the controller or put it into a service class if it's going to be reused in other places.

I don't think it's a good idea putting it on the repository unless it's not generic. Which it should be because in my opinion generic repositories rock!

John Farrell · Accepted Answer · 2011-01-18T17:52:54.233

I would never put transformation code into your repository.

Repositories abstract data access from other concerns. Views abstract
UI formatting from other concerns.

Mixing the two is just throwing all of your careful decoupling away.

The book definition of MVC strongly implies transformation should be done inside the controller:

"The controller receives input and initiates a response by making calls on model objects. A controller accepts input from the user and instructs the model and viewport to perform actions based on that input."

ViewModel objects to EF model entities conversion where?

2 Answers2