Polymorphic NHibernate mappings
- by Ben Aston
I have an interface IUserLocation and a concrete type UserLocation.
When I use ICriteria, specifying the interface IUserLocation, I want NHibernate to instantiate a collection of the concrete UserLocation type.
I have created an HBM mapping file using the table per concrete type strategy (shown below). However, when I query NHibernate using ICriteria I get:
NHibernate cannot instantiate abstract class or interface MyNamespace.IUserLocation
Can anyone see why this is? (source code for the relevant bit of NHibernate here (I think))
My ICriteria:
var filter = DetachedCriteria.For<IUserLocation>()
.Add(Restrictions.Eq("UserId", userId));
return filter.GetExecutableCriteria(UoW.Session)
.List<IUserLocation>();
My mapping file:
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-lazy="true">
<class xmlns="urn:nhibernate-mapping-2.2" name="MyNamespace.IUserLocation,MyAssembly" abstract="true" table="IUserLocations">
<composite-id>
<key-property name="UserId" column="UserId" type="System.Guid"></key-property>
<key-many-to-one name="Location" column="LocationId" class="MyNamespace.ILocation,MyAssembly"></key-many-to-one>
</composite-id>
<union-subclass table="UserLocations" name="MyNamespace2.UserLocation,MyAssembly2">
<property name="IsAdmin" />
</union-subclass>
</class>
</hibernate-mapping>
