nhibernate auditing with events on update

Question

The following code works on insert but on update modifier is never set, any ideas why?

The code for pre-update is being run and correctly sets the state and entity values to the desired value. However when viewing the generated sql nhibernate does not include the field in the update query.

/// <summary> Updates auditable objects </summary>
public class AuditEventListener : IPreInsertEventListener, IPreUpdateEventListener
{
    private ISecurityManager securityManager;

    public bool OnPreInsert( PreInsertEvent args )
    {
        var auditable = args.Entity as IAuditable;
        if (auditable != null) {

            Set( x => auditable.Creator, args.Persister, auditable, args.State, SecurityManager.Identity );
            Set( x => auditable.DateAdded, args.Persister, auditable, args.State, TwentyClock.Now );
        }
        return false;
    }

    public bool OnPreUpdate( PreUpdateEvent args )
    {
        var auditable = args.Entity as IAuditable;
        if (auditable != null) {

            Set( x => auditable.Modifier, args.Persister, auditable, args.State, SecurityManager.Identity );
            //Set( x => auditable.DateModified, args.Persister, auditable, args.State, TwentyClock.Now );
        }
        return false;
    }


    /// <summary> Type safe method to update sate and entity </summary>
    private void Set<T, U>( Expression<Func<U, T>> expression, IEntityPersister persister, U instance, object[] state, T value )
    {
        var member = expression.Body as MemberExpression;
        if (member != null) {

            var index = Array.IndexOf( persister.PropertyNames, member.Member.Name );
            if (index == -1) {
                return;
            }
            state[index] = value;

            var property = (member.Member as PropertyInfo);
            if (property != null) {
                property.SetValue( instance, value, null );
            }
        }
    }

    ISecurityManager SecurityManager
    {
        get
        {
            if (securityManager == null) {
                securityManager = KernelContainer.Kernel.Get<ISecurityManager>();
            }
            return securityManager;
        }
    }

}

Answer 1

I've answered this question here http://stackoverflow.com/questions/3164655/nhibernate-auditing-with-events-on-update