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

Question

when i try to attach entity to context i get an exception

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

This is expected behaviour.

But i would like to know how ObjectStateManager knows that? I would like to do this check by myself before

Answer 1

If you are using DbContext API (you mentioned ef-code-first) you can simply use:

context.YourEntities.Local.Any(e => e.Id == id); 

or more complex

context.ChangeTracker.Entries<YourEntity>().Any(e => e.Entity.Id == id); 

In case of ObjectContext API you can use:

context.ObjectStateManager.GetObjectStateEntries(~EntityState.Detached)                           .Where(e => !e.IsRelationship)                           .Select(e => e.Entity)                           .OfType<YourEntity>()                           .Any(x => x.Id == id); 

Answer 2

Here's an extension method for getting the object from the context without having to worry about whether it is already attached:

public static T GetLocalOrAttach<T>(this DbSet<T> collection, Func<T, bool> searchLocalQuery, Func<T> getAttachItem) where T : class {     T localEntity = collection.Local.FirstOrDefault(searchLocalQuery);      if (localEntity == null)     {         localEntity = getAttachItem();         collection.Attach(localEntity);     }      return localEntity; } 

Just call:

UserProfile user = dbContext.UserProfiles.GetLocalOrAttach<UserProfile>(u => u.UserId == userId, () => new UserProfile { UserId = userId });