NHibernate One-To-One Relationships not saving correctly

Question

I am having an issue with saving entities with one-to-one relationships. I just want to save the parent entity and have the child be save aswell but I am having to save both separately.

This is an example of what I am having to do, otherwise the child is not saved.

 var session = SessionProvider.OpenSession.Session;
            using (var tx = session.BeginTransaction())
            {
                try
                {
                    session.SaveOrUpdate(parent);
                        if (parent.Child.IsPersisted)
                        {
                            session.Update(parent.Child);
                        }
                        else
                        {      
                            session.Save(parent.Child);
                        }
                    }
}


<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-lazy="false" assembly="xxx">
  <class name="Parent" polymorphism="explicit" table="Parent">
    <id name="Id" column="JointID" type="int">
      <generator class="native" />
    </id>
    <one-to-one name="Child" class="Child" />
  </class>
</hibernate-mapping>


<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-lazy="false"
                   assembly="xxx">
  <class name="Child" xmlns="urn:nhibernate-mapping-2.2" polymorphism="explicit" table="Child">
    <id name="Id" column="JointID" type="int" unsaved-value="0">
      <generator class="native" />
    </id>
    <many-to-one name="Parent" column="JointID" insert="false" update="false" />
  </class>
</hibernate-mapping>

Any ideas on how I can just make it save without having to do two save calls?

When I set the relationship to cascade as suggested below I get foreign key constraint errors. If I analyse the queries with NHProf, its trying to use the temporary id (-1) as the JointId in the insert statement rather than the newly created parent id. The JointId in the Parent table is an Identity key, perhaps that is an issue?

Answer 1

You'll need to enable cascading on your <one-to-one> mapping to have this work properly.

Something like:

<one-to-one name="Child" class="Child" cascade="save-update" /> 

You can read up on the various cascade settings here.