Question

I’ve got a many-to-many association between Lists and ListItems: a List knows about its Items, but a ListItem doesn’t know about the containing lists. The cascade is saveupdate.

So, whenever I’m trying to delete a ListItem entity, I’m getting an SQLException saying I’m breaking the referential integrity. NHibernate tries to delete my ListItem without deleting the corresponding row in the linking table. The question is, is it possible to instruct NHibernate to delete my ListItem without breaking the referential integrity?

In case I have to manually remove the item from all containing lists, how do I properly do that?

Thanks a lot for any advice.

ulu

Answer 1

You need to set the mapping on the child to inverse=true. From another thread:

When you call SaveOrUpdate NHibernate
first deletes all of the child
objects. Then, because neither
relationship is marked as inverse,
NHibernate also tries to set the
foreign key column in your child table
to null. Since the rows have already
been deleted, you receive the second
error. You need to set inverse=true on
one side of your relationship to fix
this. This is usually done on the one
(primary key or parent) side. If you
do not do this, NHibernate will make
the appropriate updates for each side
of the relationship.

public class StoreMap : ClassMap<Store>
{
  public StoreMap()
  {
    Id(x => x.Id);
    Map(x => x.Name);
    HasMany(x => x.Staff)
      .Inverse()         // Magic code!
      .Cascade.All();
  }
}