How can I make a where clause on a reference in fluent-nhibernate mapping - nhibernate

Question

There exists such a method on HasMany and HasManyToMany but for some reason there isn't such a mechanism on References.
We have an object that references an other object that can be updated and saved as new versions but from our child object we doesn't really care we only want to load the latest version of the related object. The mapping cannot use the primary key for the related object since this will change for each version of the object so instead we want to map the related object to an property that doesn't change between versions and then make a where-clause to only selected the matching element with the highest version.
So our mapping is like the following
References(p => p.RelatedObjectIdentifier).PropertyRef("MatchingPropIdentifier").Not.Nullable;
We would like to do something like this
References(p => p.RelatedObjectIdentifier).PropertyRef("MatchingPropIdentifier").Where(p => p.IsLatest).Not.Nullable;
Of course we would update the property IsLatest (bool property) for each saving of the related object.
So since the Where(p => p.IsLatest) doesn't exist on a References for a classmap/subclassmap how can we make this happen in any other way?

Answer 1

You can only use the Where() restriction, which:
Defines a SQL 'where' clause used when retrieving objects of this type.
on the class map of the referenced type.
Example:
public class RelatedObjectMap : ClassMap<RelatedObject>
{
public RelatedObjectMap()
{
Table("RelatedObjectTable");
//Id() etc.
Where("MatchingPropIdentifier IS NOT NULL)");
}
}