Service layer ModelState not updating in .net Web API

Question

I'm implementing an MVC solution that has some Web API endpoints for various data queries. I'm using the techniques described in this post to separate my validation concerns to a Services layer.

This post has a TL;DR at the end if you want to skip to the specific question.

Here is my ApiController code:

[Authorize]
public class FriendsController : ApiController
{
    private IItemService _service;

    public FriendsController()
    {
        _service = new ItemService(new HttpModelStateWrapper(ModelState), new ViewModelRepository());
    }

    public FriendsController(IItemService service)
    {
        _service = service;
    }

    // GET api/friends
    public IEnumerable<User> Get()
    {
        return _service.GetFriends(User.Identity.Name);
    }


 .
 .
 .

    // POST api/friends
    public void Post(Guid id)
    {
        var user = _service.AddFriend(User.Identity.Name, id);  // Handles error and should update ViewModel
        NotificationAsyncController.AddNotification(user);
    }
}

and the code for _service.AddFriend(User.Identity.Name, id); looks like this:

    public User AddFriend(string userName, Guid id)
    {
        try
        {
            return _repository.AddFriend(userName, id);
        }
        catch (Exception e)
        {
            _validationDictionary.AddError("AddFriend", e.Message);
            return null;
        }
    }

And _validationDictionary looks like this:

public class HttpModelStateWrapper : IValidationDictionary
{
    private ModelStateDictionary ModelState;

    public HttpModelStateWrapper(ModelStateDictionary ModelState)
    {
        this.ModelState = ModelState;
    }

    public void AddError(string key, string errorMessage)
    {
        if (ModelState != null)
            ModelState.AddModelError(key, errorMessage);
    }

    public bool IsValid
    {
        get { return ModelState == null ? false : ModelState.IsValid; }
    }
}

Well, I found out that if _repository.AddFriend(userName, id); throws an error and _validationDictionary.AddError("AddFriend", e.Message); is called, the ModelState object that is in _validationDictionary does not update the ModelState object that resides in the FriendsController.

In other words, after AddError is called, the ModelState in the HttpModelStateWrapper is not valid, but once that method returns and scope is returned to the FriendsController, its ModelState has not updated and is still valid!

TL;DR

How do I get the ModelState object that I've passed into the HttpModelStateWrapper in the ctor of the FriendsController have its changes reflected in the ModelState object of the FriendsController?

Answer 1

I ended up just passing the whole controller and that gave me access to the ModelState object