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Hi I have a one to many ComplianceSet -> ComplianceItem. ComplianceItem has a one to many ComplianceItem -> ComplianceItemInstance.

I have

ComplianceSet

HasMany(x => x.GetUserComplianceItems()).Inverse().Access.CamelCaseField(Prefix.Underscore).LazyLoad().Cascade.AllDeleteOrphan();

And

ComplianceItem

HasMany(x => x.GetUserComplianceItemInstances()).Inverse().Access.CamelCaseField(Prefix.Underscore).LazyLoad().Cascade.AllDeleteOrphan();

Then in my code I have

userComplianceSet.GetUserComplianceItems().FirstOrDefault(....); ... userComplianceItem.RemoveUserComplianceItemInstance(userComplianceItemInstance);

this code returns

deleted object would be re-saved by cascade (remove deleted object from associations)[DecisionCritical.Core.Domain.UserComplianceSet#12]

Now this is very frustrating. If I remove the cascade from both collections the code returns success but the db show's that it didn't do anything. the ComplianceItemInstance.ComplianceItemId field is still populated and of course the item is still there. In anycase, I just want to be able to delete a child from a collection, call save on the object holding the collection and have the freakin thing go away. I've tried all manner of permutations of cascade, save ( saving the set, saving the item ) adding delete to the ComplianceItemInstance and so and can't get this to work.

Please help

Raif
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  • What's the code of RemoveUserComplianceItemInstance? – Ilya Kogan Apr 19 '11 at 21:09
  • Ok so I figured out what the issue is and I think Ilya was about to point me in this direction. because this is a bi-directional relationsip I must set the UserComplianceItemInstance.UserComplianceItem = null before saving the parent. – Raif Apr 20 '11 at 16:01
  • Now I tried all manner of things, one of which was to make it a unidirectional reference, however, ( and I didn't know this at the time ) if the fk is set to not null in the db table a unidirectional reference wont work because it saves the child with a null fk then does an update of the child with the fk. I was getting the 'can't insert null in fk' error and assuming I was on the wrong track. Anyway, all better now. albeit a couple days of life less. Can I mark plus one for figuring out my own answer? :) – Raif Apr 20 '11 at 16:07
  • yes, you can answer your own question and select your answer as the accepted one, and it's even encouraged. See here: http://meta.stackexchange.com/questions/17845/etiquette-for-answering-your-own-question and here: http://meta.stackexchange.com/questions/12513/should-i-not-answer-my-own-questions and here: http://meta.stackexchange.com/questions/17463/should-i-ask-a-question-i-know-the-answer-to – Ilya Kogan Apr 21 '11 at 05:37

1 Answers1

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I have been struggling with the same thing. Reaction is a bit late, but maybe future readers can benefit.

The solution of allowing null as foreign key on the child table works, but it might not be desirable from a database design point of view if your child cannot exist without a parent anyway. Modifying the database design purely because NHibernate requires it, is not something I prefer. Also changing from bidirectional to unidirectional was undesirable for me. So I dove in and tried all sorts of combinations of mappings.

What I found out is that using inverse = true fixed the problem. First I thought this was bad behavior from NHibernate, since inverse = true is mostly explained as making the child collection responsible for the relation, which I thought I already covered by manually updating both child and parent. But this responsibility is more of a database thing than anything else.

Using inverse = true, it is still possible to delete a child by removing it from the parent, as long as you have Cascade.AllDeleteOrphan on the parent-side of the mapping, everything will be correctly updated. If you choose to use Cascade.All, you must also explicitly delete the child.

If the parent is not loaded you can also choose to delete the child immediately, simply by deleting it in the current session. But this does not work if the parent is loaded in which case it will give the cascade re-save issues.

Bottom line for me is, inverse works. And I have not found a scenario in which inverse = false gives me better results, but I might get back to that opinion once diving deeper into NHibernate.

Leroy
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