NHibernate - Save child - only set key from Parent

Question

Hi.

I have the fallowing problem: I have to tables SalesHeader and SalesPosition - where SalesPosition is a child of SalesHeader. Now. In table SalesHeader, there is a persistent Entity X. I try now to persist an Entity in SalesPosition with only give this Entity the Key to X (of SalesHeader). NHibernate does not have to save some data in SalesHeader. Now, when I flush the entity to SalesPosition, I become the fallowing exception:

object references an unsaved transient instance - save the transient instance before flushing.

at NHibernate.Engine.ForeignKeys.GetEntityIdentifierIfNotUnsaved(String entityName, Object entity, ISessionImplementor session) at NHibernate.Type.EntityType.GetIdentifier(Object value, ISessionImplementor session) at NHibernate.Type.ManyToOneType.IsDirty(Object old, Object current, Boolean[] checkable, ISessionImplementor session) at NHibernate.Type.TypeFactory.FindDirty(StandardProperty[] properties, Object[] x, Object[] y, Boolean[][] includeColumns, Boolean anyUninitializedProperties, ISessionImplementor session) at NHibernate.Persister.Entity.AbstractEntityPersister.FindDirty(Object[] currentState, Object[] previousState, Object entity, ISessionImplementor session) at NHibernate.Event.Default.DefaultFlushEntityEventListener.DirtyCheck(FlushEntityEvent event) at NHibernate.Event.Default.DefaultFlushEntityEventListener.IsUpdateNecessary(FlushEntityEvent event, Boolean mightBeDirty) at NHibernate.Event.Default.DefaultFlushEntityEventListener.OnFlushEntity(FlushEntityEvent event) at NHibernate.Event.Default.AbstractFlushingEventListener.FlushEntities(FlushEvent event) at NHibernate.Event.Default.AbstractFlushingEventListener.FlushEverythingToExecutions(FlushEvent event) at NHibernate.Event.Default.DefaultFlushEventListener.OnFlush(FlushEvent event) at NHibernate.Impl.SessionImpl.Flush() at NHibernate.Transaction.AdoTransaction.Commit()

this is my mapping of SalesPosition:

<class name="SalesPosition" table="SalesPosition" lazy="false"  >
    <id name="Id" column="Id" type="Guid">      
                    <generator class="assigned"/>
    </id>
  <version name="ObjectVersion" column="ObjectVersion"/>
  .... some fields
    <many-to-one  name="SalesHeader" class="SalesHeader" foreign-key="FK_SalesHeader_SalesPosition" >
        <column name="SalesHeaderId"/>
    </many-to-one>
</class>

and this is the mapping of SalesHeader:

<class name="SalesHeader" table="SalesHeader" lazy="false"  >
    <id name="Id" column="Id" type="Guid">      
                    <generator class="assigned"/>
    </id>
  <version name="ObjectVersion" column="ObjectVersion"/>
... some fields
    <set name="SalesPosition" lazy="true" inverse="true" cascade="delete" >
        <key>
            <column name="SalesHeaderId"/>
        </key>
        <one-to-many class="SalesPosition"/>
    </set>
</class>

Can anybody give me a tip, what I have to do, that I can only give the key of SalesHeader to the SalesPosition-Entity for persisting (or the SalesHeader-Entity and NHibernate is only using the key).

I use the newest release Version of NHibernate.

Thank you.

Best Regards, Thomas

Answer 1

If I understand your question correctly, you are attempting to save a SalesPosition instance but you want to just set SalesPosition.SalesHeader.Id instead of setting SalesPosition.SalesHeader to an instance of SalesHeader. You can accomplish this using ISession.Load; this posting explains how it works. Basically, if you know that an entity exists in the database, you can use Load to create a proxy for the object rather than getting it from the database. This is very handy in stateless (web) applications. Usage will be:

mySalesPosition.SalesHeader = session.Load<SalesHeader>(salesHeaderId);
session.Flush();