Question

Is there any way to get NHibernate to let me store multiple ChildObjects in the ChildObjectTable but refer them back to different ParentObjects? Or do I have to create a separate ChildObject class/table for each ParentObject type?

I’ve boiled this down to the following, I’m trying to map these objects:

public class ParentObjectA {     public virtual Int64 Id { get; private set; }      public virtual IDictionary<int, ChildObject> Children { get; private set; } }  public class ParentObjectB {     public virtual Int64 Id { get; private set; }      public virtual IDictionary<int, ChildObject> Children { get; private set; } }  public class ChildObject {     public virtual Int64 Id { get; private set; }    } 

into the following table structure:

ParentObjectTableA   Id bigint  ParentObjectTableB   Id bigint  ChildObjectTable   Id bigint   ParentId bigint   ParentQualifier varchar(50) 

Answer 1

The following maps seem to work from an object perspective. I’m not overly keen on the idea of using crosstables, but I think this might be cleaner than trying to deal with inheritance. I’m going to take a look at that option as well and I’ll post my findings here for the sake of completion. Comments welcome.

Mapping of ParentObjectA

<map name='Children' table='ParentAxChildObject'>     <key column='ParentId' />     <index column='ChildObjectNumber' type='Int32' />     <many-to-many class='ChildObject' /> </map> 

Mapping of ParentObjectB

<map name='Children' table='ParentBxChildObject'>     <key column='ParentId' />     <index column='ChildObjectNumber' type='Int32' />     <many-to-many class='ChildObject' /> </map> 

These generate the following cross tables:

ParentAxChildObject     [ParentId] [bigint] NOT NULL,     [elt] [bigint] NOT NULL,     [ChildObjectNumber] [int] NOT NULL,  ParentBxChildObject     [ParentId] [bigint] NOT NULL,     [elt] [bigint] NOT NULL,     [ChildObjectNumber] [int] NOT NULL,