How to configure NHIbernate event listeners for Update and Save?

Question

Following on from my previous question How to implement LastUpdate in NHibernate Entities?.

I have two columns on my audited tables in my database:

created datetime default getdate() not null (the creation date of this row)
lastUpdate datetime null (the datetime this row was last updated)

I want to create a listener for updates only in NHibernate, because the database engine takes care of new records with the default constraint. I tried to create a Custom listener with this code:

public class CustomUpdateEventListener : DefaultSaveOrUpdateEventListener
{
    protected override object PerformSaveOrUpdate(SaveOrUpdateEvent evt)
    {
        var entity = evt.Entity as IAuditableEntity;
        if (entity != null)
        {
            ProcessEntityBeforeUpdate(entity);
        }
        return base.PerformSaveOrUpdate(evt);
    }

    internal virtual void ProcessEntityBeforeUpdate(IAuditableEntity entity)
    {
        entity.UpdateDate = DateTime.Now;
    }
}

and it works great for updates, but it also gets run for Save events (when I add new rows to the database). I don't want it to fire for new rows. I tried to change the code to listen to Update events only but I can't work it out.

I tried to change the class to inherit from DefaultUpdateEventListener but there's no UpdateEvent (only SaveOrUpdate events or PreUpdate or PostUpdate)

I'm wondering if I should use the PreUpdate event and making my listener inherit from DefaultUpdateEventListener but then I'm not sure which method I need to override. There is no Update method to override.

I know this is an old post but did you come across this blog post? http://ayende.com/blog/3987/nhibernate-ipreupdateeventlistener-ipreinserteventlistener — Rippo, Dec 02 '12 at 08:23

score 2 · Answer 1 · answered Jan 15 '12 at 20:34

2

You could make your class implement the IPreUpdateEventListener interface (and its OnPreUpdate method). Then add your class to the session event listerners through the config:

NHibernate.Cfg.Configuration cfg = new NHibernate.Cfg.Configuration();
cfg.EventListeners.PreUpdateEventListeners = 
    new IPreUpdateEventListener[] {new YourEventListener()};
sessionFactory = cfg.BuildSessionFactory();

answered Jan 15 '12 at 20:34

Wiz101

138
7

Which class would implement that? My `Update` method in my DAL? Or my base entity class? Where would that config code go? – Mark Allison Jan 16 '12 at 08:50
You could implement this in your CustomEventUpdateListener class. The code above wires up a session factory with this event listener. You then create your NHibernate session from this factory and the OnPreUpdate method of the listener will get called for each entity that is about to be updated (through a Flush on the session). – Wiz101 Jan 16 '12 at 20:19

score 1 · Answer 2 · answered Jan 01 '14 at 17:47

It appears that there is a PerformUpdate event that can be overridden from the DefaultSaveOrUpdateEventListener class

protected override void PerformUpdate(NHibernate.Event.SaveOrUpdateEvent @event, object entity, NHibernate.Persister.Entity.IEntityPersister persister)
{
    base.PerformUpdate(@event, entity, persister);
}

How to configure NHIbernate event listeners for Update and Save?

2 Answers2

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