R – NHibernate: difference between Interceptor and Listener

I've worked around this problem by adding a list to my interceptor class which is populated with objects during the OnSave implementation.

In the PostFlush implementation the list is iterated over and each element is audited as an insert. The objects in this list have been persisted in PostFlush() and thus have generated IDs.

This seems to work OK but I'd be grateful if any potential pitfalls were pointed out :-)

public class AuditInterceptor : EmptyInterceptor
{       
    // To hold inserted items to be audited after insert has been flushed
    private IList<object> insertItems = new List<object>();

    public override void PostFlush(System.Collections.ICollection entities)
    {            
        foreach (var entity in insertItems)
        {
            AddAuditItem(entity, INSERT);
        }
        insertItems.Clear();

        base.PostFlush(entities);
    }

    public override bool OnSave(object entity, object id, object[] state, 
        string[] propertyNames, IType[] types)
    {            
        var auditable = entity as IAuditable;
        if (auditable != null) 
            insertItems.Add(entity);

        return false;            
    }
}

An interceptor allows you to execute additional functionality when an entity is retrieved / deleted / updated / inserted in the DB ...

Interceptors article

Hibernate doc

other useful info

About making your app slower: I'd suggest that you only have a look at optimizing start-up time, when it really becomes a problem.

When you build a session-factory, NHibernate will parse all the mappings, and that is an operation that is a bit expensive. But, as long as you have a limited number of entities, the performance hit isn't that big.
I have never ever had to optimize the initialization of NHibernate, because of slow startup times.

I'd suggest that you first concentrate on the core of your application -the problem you're trying to solve- and afterwards have a look on how you could improve startup performance. (If you'll ever have to do it).