Fluent NHibernate subclass reference

Question

So I have following entities:

TimelineRecord:
    ID: PK
    From: DateTime
    To: DateTime

ServiceRecord extends TimelineRecord:
    ID: PK
    TimelineRecord_ID: FK
    SomeSpecificProperties...

Demand:
    ID: PK
    From: DateTime
    To: DateTime
    ...

ServiceDemandConnection:
    ID: PK
    Service: ServiceRecord
    Demand: Demand

TimelineRecord, Demand and ServiceDemandConnection are mapped using ClassMap with Id(x => x.Id). ServiceRecord is mapped using SubclassMap (table-per-class). References in ServiceDemandConnection are mapped using References(x => x.Service).Cascade.None() and the same for .Demand.

The problem is with inserting ServiceDemandConnection with properly set ServiceRecord and Demand. I get an error: Detail=Key (servicerecord_id)=(8) is not present in table "ServiceRecord". What error states is true. 8 is the ID of TimelineRecord, not ServiceRecord. However, ID of ServiceRecord (TimelineRecord_ID, which is actually not mapped/not accessible in the code) should be used instead. The current mapping hides ServiceRecord.ID.

How should I tell NHibernate to use ID of the subclass table (ServiceRecord), and not of the base class table (TimelineRecord)? NHibernate actually creates a proper constraint in the database, but during runtime it violates it somehow.

tchrikch tchrikch · Accepted Answer · 2015-04-01T14:09:42

You need to either

map ServiceRecord as separate class not using SubclassMap to use it's ID
or use ID from base class and do not map it inside SubclassMap

The second approach works because SubclassMap creates a FK relationship between child and parent object so that data is consistent and you have something like

TimeLineRecord
  ID : PK

ServiceRecord extends TimelineRecord:
  TimelineRecord_ID: FK -----> TimeLineRecord.ID

It is still valid to point references to child classess.

Fluent NHibernate subclass reference

1 Answers