fluent nhibernate mapping with not null foreign key (HasMany)

Question

I have the following mapping in nhibernate. When I call Session.Merge(myparent) I get the an error on the insert indicating that NULL cannot be inserted into the foreign key (ParentItemId) column.

How can I adjust the mapping so that the parent key is inserted on insert. If I make the foreign key nullable this mapping works, but two separate statements are issued to the database.

This relationship is a one to many without a reference back to the parent on the child class.

The child class has no parent property.

The child is dependent on the parent.

HasMany(map => map.Children).Table("ChilrenTable")
   .KeyColumn("ParentItemId") // this is not nullable.
   .Cascade
   .AllDeleteOrphan();

example update

// entity here is the parent instance, which contains the list
// of children.
using (var tx = Session.BeginTransaction())
{
    entity = Session.Merge(entity); // this line causes the problem.
    Session.SaveOrUpdate(entity);
    Session.Flush();
    tx.Commit();
    return entity;
}

score 3 · Accepted Answer · edited May 23 '17 at 11:51

3

Inverse Attribute in NHibernate

HasMany(map => map.Children).Table("ChilrenTable")
   .KeyColumn("ParentId") // this is not nullable.
   .Inverse()  // <--- This is the key here
   .Cascade
   .AllDeleteOrphan();

edited May 23 '17 at 11:51

Community

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answered Sep 12 '12 at 11:43

Cole W

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I tried this, but the merge is still failing. Perhaps it has something to do with the merge. I am merging changes back to the database from posted web data that is being sent to a WCF service. The WCF service is merging and updating the data. It still attempts to insert a null value, and then subsequently updates the foreign key value. – Jim Sep 13 '12 at 05:02
Reading a little further, it would seem that perhaps inverse only works with bi-directional relationships. In my case the relationship is not bi-directional. The parent owns the child items, but the child items have no parent property and hence no nhibernate mapping to the parent. – Jim Sep 13 '12 at 05:10
@Jim Maybe you should make it a bidirectional relationship. – Cole W Sep 13 '12 at 12:36
Hi Cole, that's what I am beginning to think as well. The reason I have not is that the serialization over WCF can be an issue with circular relationships. I think I will use bi directional relationships and mark all the data contracts as IsReference = true. – Jim Sep 13 '12 at 14:52

fluent nhibernate mapping with not null foreign key (HasMany)

1 Answers1