I have a collection mapped as a bag:



There is a business method within the MemberSurvey class that removes an element from the collection:



Using log4net, I can see that elements are in fact being deleted from the collection. However, when the session is flushed (or when I call update on the MemberSurvey object) NH is executing an UPDATE statement instead of a DELETE:



I may not be understanding the cascade property but I thought "all-delete-orphan" would immediately cascade operations on the collection without calling session.flush for one, and the second question is, why does a call to IList.Remove() translate into an UPDATE call on the DB. Shouldn't that be a DELETE? I think I'm doing something wrong...

comments are appreciated.

-devon

Does it try to execute a DELETE afterwards? It may just be the way NHibernate works. Since you deleted the object from the collection, NHibernate just removes the association, but does not remove the object itself. Then the cascade should come into play and remove the entire object.

The reason is you might want to move a question to another survey and NHibernate should be prepared to handle that (even though this usage is actually quite rare in real applications).

You can try removing the question and calling Delete on it manually afterwards.

thanks for the clue on the internals of NH. that helps in my understanding. in this instance, setting inverse="true" on the bag worked. I guess i'm still not completely understanding the inverse="true" setting...

-d

I think inverse="true" basically means that the objects in the collection only exist as part of the parent.

For example, and Invoice has InvoiceLines. You can't have invoice lines without an Invoice. So, InvoiceLines would be inverse=true. So, when the Invoice is deleted, so are the LineItems.

But, think of Tennent / Unit... The tennent lives in a unit. But, if the tennent moves out the relation ship is broken, but there is still a Unit. The Tennet either moves to a different Unit or he goes away. You wouldn't want to delete the Unit just cause you delete the Tennent.

Another way perhaps to think about it is, if the FK in the child table of the relation ship field allows nulls, the inverse=false. If the FK in the child table is required then you have inverse=true. Of course, there are probably exceptions to this rule.

At least, that is my small minds understanding of them.

BOb