NHibernate: Query by discriminator on association - nhibernate

Question

My question is similar to this question.
But I want to query by the discriminator of a child entity associated with a one-to-one relationship, and without knowing the exact discriminator value, i.e., by type not by string.
Given an hbm like:
<class name="Parent" table="ParentTable">
<id name="Id">
<generator class="guid.comb" />
</id>
<one-to-one name="Child" class="IChild" property-ref="Parent" cascade="all" />
</class>
<class name="IChild" table="ChildTable" abstract="true">
<id name="Id">
<generator class="foreign">
<param name="property">Parent</param>
</generator>
</id>
<discriminator column="TypeKey" type="String"/>
<one-to-one name="Parent" class="Parent" />
</class>
<subclass name="ConcreteChild" extends="IChild" discriminator-value="Concrete1">
<property name="SomeProperty"/>
</subclass>
Or any other one-to-one configuration, I would like to run a query similar to this:
public IEnumerable<Parent> FindByChild(Type childType)
{
return session.CreateCriteria<Parent>()
.Add(Restrictions.Eq("Child.class", childType))
.List<Parent>();
}
Further information:
The above criteria query fails because "Child.class" is not recognized as valid.
A similar query using HQL fails because NHibernate uses the fullname of childType rather than its discriminator value in the query.

Answer 1

Have you tried using an alias? I can't test it right now on my machine, but should be similar to this..
return session.CreateCriteria<Parent>()
.CreateAlias("ParentChild","Child")
.Add(Restrictions.Eq("ParentChild.class", childType))
.List<Parent>();
where ParentChild is just the name I used to refer to the Child entity of the Parent class