Why is AutoMapper/EF adding a new item instead of a relationship?

Question

I have this test in my test base:

public void WorksWithAreaUsers()
     {
      using (new TransactionScope())
      {
       //arrange
       var userBusiness = new UserBusiness();
       var user = new User
       {
        Name = "TestUser###",
        Login = "domain\test-user###"
       };
       userBusiness.Add(user);

       var areaBusiness = new AreaBusiness();
       var area = new Area
       {
        Name = "TestArea###",
        Description = "Test Area Description",
        Users = new List<User> { user }
       };

       //act
       areaBusiness.Add(area);

       //assert
       var areaFromDb = areaBusiness.FindById(area.AreaID);
       Assert.IsNotNull(areaFromDb.Users);
       Assert.IsTrue(areaFromDb.Users.Count > 0);
       Assert.IsTrue(areaFromDb.Users.Any(c => c.UserID == user.UserID));
      }
     }

What it is doing:

• Inserts a new user into the base;
• Inserts a new area into the base, with the user relationship;

What actually happens:

• The new user is inserted;
• The new area is inserted;
• The new user is inserted again, with area relationship;

What can be happening?

More information:

• Area and User aren't EntityObjects really. I am mapping DTO/Entity using AutoMapper, I think the problem is in this logic. In a certain moment, I have to map between the List and the EntityCollection. I create a new EntityCollection and put the User converted into a UserEntity in this collection, using the EntityCollection.Add method. I think I should use Attach in order to not create a new entity, but this method doesn't work when called from an EntityCollection without the proper bindings.

Do you suggest anything clever than that, or any workaround to solve this issue? I really need the project layers (Web -> Business -> Data -> EF), asp.net working directly with EF is something we can't do here, for modularity reasons.

EDIT:

I'm giving up the idea of using AutoMapper to do this job =/ I don't have a lot of entities, and the changes I need to do in this library in order to work requires some effort, it isn't something trivial to do. It is better to do the mapping by myself.

Answer 1

I assume your User object has an Area property that can also be used to establish the relationship between the entities. Instead of setting Area.Users equal to a new list, after you create the area object just set User.Area equal to the new area. This is how I handle associating new entities and it works reliably.

EDIT

If I understand what you are doing, you are creating business objects (BOs) that later create entity objects (EO) and attach those EOs to a context and save them.

Assuming I have the basics correct, determing the exact cause of you problem requires seeing the code for how the respective BOs create EOs and attach them to the context.

Answer 2

My guess (and it is just a guess) is that AutoMapper isn't doing identity resolution

So when it sees the same object (user) in different places in the graph it creates a new object rather than re-using the object it created previously.

This would probably explain what you are seeing.

Alex