Removing Objects With a Relationship from DbContex

Question

I recently started learning Entity Framework and OData, and while there has been a learning curve, most problems seemed possible to solve without asking for help. This problem that I have has stumped me for over a day and I cannot find in the documentation what I am looking for.

The project is a simple Movie Database; Movies have a director and actors, and 'Film Professionals' have directing and acting credits for movies. When I try to delete a movie though, either I get an error saying:

"Adding a relationship with an entity which is in the Deleted state is not allowed."

or everything runs without throwing an error, but the state of the actors/director are reverted back to where they were before the delete call.

Here is the code that I am working with:

protected IHttpActionResult OnDelete(int key)
    {
        if (!Initialized) return NotFound();
        var entity = DeleteOperation(key, DbContext);
        if (entity == null) return NotFound();
        DbSet.Remove(entity);
        DbContext.SaveChanges();
        return StatusCode(HttpStatusCode.NoContent);
    }

protected override Movie DeleteOperation(int key, MovieContext movieContext)
    {
        var removeMovie = movieContext.Movies.FirstOrDefault(key, true, "Cast", "Director");
        if (removeMovie == null) return null;

        if (removeMovie.Cast != null)
        {
            foreach (var actor in removeMovie.Cast)
            {
                actor.Actor =
                    movieContext.Movies.Any(m => m.Key != removeMovie.Key && m.Cast.Any(c => c.Key == actor.Key));
            }
        }

        if (removeMovie.Director != null)
        {
            removeMovie.Director.Director =
                movieContext.Movies.Any(m => m.Key != removeMovie.Key &&
                                             m.Director.Key == removeMovie.Director.Key);
        }

        return movieContext.Movies.FirstOrDefault(key, false);
    }


public static T FirstOrDefault<T>(this DbSet<T> dbset, int key, bool disableTracking, params string[] include)
        where T : ModelBase
    {
        if (dbset == null) return null;
        var query = disableTracking ? dbset.AsNoTracking() : dbset.AsQueryable();
        if (include.Length <= 0) return query.FirstOrDefault(e => e.Key == key);
        var i = 1;
        try
        {
            for (i = 0; i < include.Length; i++)
            {
                query = query.Include(include[i]);
            }
            return query.FirstOrDefault(e => e.Key == key);
        }
        catch (Exception)
        {
            throw new Exception("Include value '" + include[i] + "' has no context");
        }
    }

I have a feeling the actor/director state reverting back has to do with the call of .AsNoTracking() on my database context, but without doing that, I get the aforementioned error every time. From my understanding, I need to essentially detach both Cast and Director from the Movie entity, but I don't know the proper syntax.

Answer 1

So the solution that I came up with was to create a new instance of the database context within a using statement. The problem was that I was using the same instance of the database context for the DeleteOperation as I was in the OnDelete. This cleared up all errors and let me save the changes to the entities.