Question

BACKGROUND

I’m having some trouble with updating an entity in EF. I keep getting this error:

“An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key”

I am fully aware that there is obviously another entity somewhere that is attached. However, I currently cannot track it down. There is a lot of code and I’ve spent quite some time on it already. As far as I can see, I am using the AsNoTracking() extension method on all my queries.

WHAT I NEED

My question is this: Is there any way I can see what is actually in the ObjectStateManager at any given time? If I can see the items in there during debugging, I can more quickly track down where this is coming from.

If the above is not possible, I would appreciate any advice on how best to tackle this problem.. it’s like a needle in a haystack right now.

Answer 1

This question helped:

what is the most reasonable way to find out if entity is attached to dbContext or not?

and I implemented it in this way:

var attachedEntity = context.ChangeTracker.Entries<T>().FirstOrDefault(x => x.Entity.Id == entity.Id);

                // If the entity is already attached. 
                if (attachedEntity != null)
                {
                    // Set new values
                    attachedEntity.CurrentValues.SetValues(entity);
                }
                else
                {
                    // Else attach the entity (if needed)
                    if (context.Entry(entity).State == EntityState.Detached)
                    {
                        Entities.Attach(entity);
                    }
                    // Set the entity's state to modified
                    context.Entry(entity).State = EntityState.Modified;
                }
                context.SaveChanges();

Note: Entities is just IDbSet<T> from context.Set<T>() and the code above is from the Update() method in my generic repository.