无法使用POCO更新Entity Framework 4中的实体

Question

I have 2 tables : Item and Location (one - many ).

I select one location and I try to update it

The entity goes from {Id=2, Name="name1",City="city1",Items=null} to {Id=2, Name="name1", City="city2",Items=null} and i want to save the updates. The update method from the base class is:

        public virtual void Update(T entity)
        {
            Entities.Attach(entity);
            Context.ObjectStateManager
                   .ChangeObjectState(entity, System.Data.EntityState.Modified);
        }

I make several updates just like this on other tables with no problems but in this case I get "An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key." and I really don't understand why.

Answer 1

You can try specifying: MergeOptions.NoTracking for the context and see if that solves your problem.

Also, you can try Context.ObjectStateManager.TryGetObjectStateEntry(entity, out stateEntry) to see if the object is there and can be updated.