Fluent nHibernate mapping opposite side of References - nhibernate

Question

I've got a table structure similar to the below:
AttributeKey (ID, Title)
AttributeValue (ID, AttributeKeyID, Value)
I've got my mapping all setup so that if I query AttributeValue, it joins to AttributeKey (AttributeValue.AttributeKeyID = AttributeKey.ID) using References, no problem... however, I want to query the AttributeKey table and LEFT JOIN onto the AttributeValue table so that I get all AttributeKeys and any values ascociated to them... how do I map this in fluent nHibernate?
Essentially it's the reverse of a References mapping.
EDIT: I'm aware that the HasMany method is meant to be the reverse of References but using that throws the exception that my property doesn't implement UserCollectionType
Cheers

Answer 1

This should be a HasMany in your AttributeKey ClassMap. Your class should look something like this:
public class AttributeKey
{
public int Id { get; set; }
public string Title { get; set; }
public IList<AttributeValue> AttributeValues { get; set; }
}
Your mapping would then look like this:
public class AttributeKeyMap : ClassMap<AttributeKey>
{
public AttributeKeyMap()
{
Id(x => x.Id, "ID");
Map(x => x.Title);
HasMany(x => x.AttributeValues)
.KeyColumn("AttributeKeyID")
.Inverse()
.Cascade.AllDeleteOrphan();
}
}