Nhibernate will not delete child from collection

Question

First the mapping...

<set name="Comments" table="cm_events_venue_comment" inverse="true"
        lazy="true" generic="true" cascade="all-delete-orphan"
        batch-size="10" order-by="dateCreated ASC">
    <cache usage="read-write" />
    <key column="venueId" />
    <one-to-many class="VenueComment" />
</set>

A passing test..

    [Test]
    public void CanSaveAndDeleteComments()
    {
        User u = TestDataHelper.CreateUser("Sir", "Talkalot");
        VenueComment comment;
        Venue v = GetVenueById();

        PerformInTransaction(() =>
        {
            userRepository.SaveOrUpdate(u);
            comment = new VenueComment()
            {
                Commenter = u,
                Text = "I like ifs and buts and i cannot lie..",
                DateCreated = DateTime.Now
            };
            v.AddComment(comment);
            comment = new VenueComment()
            {
                Commenter = u,
                Text = "And words ending in 'ly'",
                DateCreated = DateTime.Now
            };
            v.AddComment(comment);
            Assert.DoesNotThrow(()=>venueRepository.SaveOrUpdate(v));
        });

        // Test retrieval 
        Session.Evict(v);

        v = GetVenueById();
        v.Comments.Count.ShouldEqual(2);
        var c = v.Comments.FirstOrDefault<VenueComment>();
        c.Commenter.Id.ShouldEqual(u.Id);

        // and deletion
        PerformInTransaction(() =>
        {
            v.RemoveComment(c);
        });

        Session.Evict(v);
        v = GetVenueById();
        v.Comments.Count.ShouldEqual(1);

    }

My problems comes in the controller of my app :

    [Authenticate, AcceptAjax]
    public ActionResult DeleteComment(int id)
    {
        return PerformInTransaction<ActionResult>(() =>
            {
                var comment = commonDao.GetObjectById<VenueComment>(id);
                if (comment == null)
                    return JsonFailure("Comment not found");

                if (comment.Commenter.Id == CurrentUser.Id ||
                    AuthUtil.IsAdministrator()) //
                {

                   var venue = comment.Venue;
                   venue.RemoveComment(comment);

                    return JsonSuccess(id);
                }
                return JsonFailure("You can only delete comments you created.");
            });
    }

According to Log4Net, no deletes were issued. As i said the above test passes, so the mapping should be correct...

Any clues ?

Answer 1

In my experience, this happens when I forget to either commit the transaction or properly close down & flush the session. Session & transaction management is also a notable difference between your test and your presenter.

Answer 2

If you take a look at the documentation for the inverse attribute on collection-type property mappings, you will find that setting inverse="false" instructs NHibernate to watch the parent object (the object containing the collection) for changes to the collection, and to insert/delete child objects based on adds/removes on the parent's children-collection.

But, when you set inverse="true", you are instructing NHibernate to watch the child object for changes to the reference property back to the parent object. So when you set the child's parent-reference property, NHibernate will then go and modify the association.

It looks like you do not want to set inverse="true" on the parent's children-collection.

Addendum:

RemoveComment may disassociate the parent from the child (as in, set child.Parent = null). But if it doesn't also disassociate the child from the Session, and if the collection is marked inverse="true" indicating that the child owns the association rather than the collection owning the association, then NHibernate will not send down a delete. NHibernate will only send down a delete if the object is supposed to be deleted - a) if a collection owns the association (inverse="false") and the collection's cascading is set to include deletions and the object is removed from the collection, or b) if the object is deleted from the Session.

Answer 3

Mystery Solved.... It was a case of the merging of two code bases..

One older dao (commonDao) had a bug where the internal Session property was creating a new session from the session factory per property access, so there was a different session between the object load and flush().

The newer code uses repositories based on S#arp Architecture, which has automatic session management, so the problem did not appear in the unit tests.