Question

I have a 1..* relationship between Review and Recommendations.

The relevant portion of my model (which is also the POCO mapped by EF4):

public class Review
{
   public ICollection<Recommendations> Recommendations { get; set; }
}

On an Edit View, i represent the Recommendations as a set of checkboxes.

When i try and add a new Recommendation as part of editing the Review (e.g check another box), nothing is happening – and i know why…

I use the “stub technique” to update my entities – e.g i create a entity with the same key, attach it to the graph, then do ApplyCurrentValues. But this only works for scalar properties, not for navigational properties.

I found this StackOverflow question which looks good, but i am trying to work out how to get this to work with POCO’s/Repository (and ASP.NET MVC – detached context).

As i’m using POCO’s, review.Recommendations is an ICollection<Recommendation>, so i can’t do review.Recommendations.Attach. I’m not using Self-Tracking Entities either, so i need to manually work with the graph/change tracking – which hasn’t been a problem until now.

So you can visualize the scenario:

Review:

• Recommendations (ICollection<Recommendation>):
  • RecommendationOne (Recommendation)
  • RecommendationTwo (Recommendation)

If im on the edit view, two of the checkboxes are already checked. The third one (representing RecommendationThree) is unchecked.

But if i check that box, the above model becomes:

Review:

• Recommendations (ICollection<Recommendation>):
  • RecommendationOne (Recommendation)
  • RecommendationTwo (Recommendation)
  • RecommendationThree (Recommendation)

And so i need to attach RecommendationThree to the graph as a new entity.

Do i need hidden fields to compare the posted data the existing entity? Or should i store the entity in TempData and compare that to the posted entity?

EDIT

To avoid confusion, here is the full app stack call:

ReviewController

[HttpPost]
public ActionResult Edit(Review review)
{
   _service.Update(review); // UserContentService
   _unitOfWork.Commit();
}

UserContentService

public void Update<TPost>(TPost post) where TPost : Post, new()
{
   _repository.Update(post); // GenericRepository<Post>
}

GenericRepository – used as GenericRepository<Post>

public void Update<T2>(T2 entity) where T2 : class, new()
{
   // create stub entity based on entity key, attach to graph.

   // override scalar values
   CurrentContext.ApplyCurrentValues(CurrentEntitySet, entity);
}

So, the Update (or Add or Delete) Repository methods needs to be called for each recommendation, depending it’s new/modified/deleted.

Answer 1

Perhaps I need more context but whats wrong with:

recommendations.Add(newRecomendation)

?

In reply to comment:

Ok so whats wrong with

SomeServiceOrRepository.AddNewRecommendation( newRecommendation )

or

SomeServiceOrRepository.AddNewRecommendation( int parentId, newRecommendation )

Last Sentence? You mean the two questions?

This shouldn’t be hard at all.

To summarize my answer I think you are doing things “the hard way” and really should focus on posting form values that correspond to the CRUD action your trying to accomplish.

If a new entity could come in at the same time as your edited entities you should really prefix them differently so the model binder can pick up on it. Even if you have multiple new items you can use the same [0] syntax just prefix the “name” field with New or something.

A lot of times in this scenario you can’t rely on Entity Frameworks graph features because removing an entity from a collection never means it should be set for deletion.

If the form is immutable you could also try using the generized attach function off of ObjectSet:

theContect.ObjectSet<Review>().Attach( review )

Tons of ways out of this. Maybe you could post your controller and view code?