<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2">
    <session-factory name="TerraCognita.LoanExpress">
        <!-- other stuff... -->
        <listener type="delete" class="Test.TestDeleteListener, MyDllName" />
    </session-factory>
</hibernate-configuration>

<hibernate-configuration   xmlns="urn:nhibernate-configuration-2.2">
    <session-factory name="TerraCognita.LoanExpress">
        <!-- other stuff... -->
        <event type="delete">
            <listener class="Test.TestDeleteListener, MyDllName" />
        </event>
    </session-factory>
</hibernate-configuration>

var cfg = new NHibernate.Cfg.Configuration();
cfg.AddAssembly("MyDllName");
sessionFactory = cfg.BuildSessionFactory();

var sess = GetSession();
sess.GetSessionImplementation().Listeners.DeleteEventListeners =
    new NHibernate.Event.IDeleteEventListener[] { new TestDeleteListener() };

var cfg = new NHibernate.Cfg.Configuration();
cfg.Configure();
cfg.AddAssembly("MyDllName");
sessionFactory = cfg.BuildSessionFactory();