Inheritance Mapping with Fluent NHibernate

Question

Given the following scenario, I want map the type hierarchy to the database schema using Fluent NHibernate.

I am using NHibernate 2.0

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Type Hier

Answer 1

I know this is really old, but it is now pretty simple to set up fluent to generate the exact mapping you initially desired. Since I came across this post when searching for the answer, I thought I'd post it.

You just create your ClassMap for the base class without any reference to your subclasses:

public class ItemMap : ClassMap
{
    public ItemMap()
    {
        this.Table("Item");
        this.DiscriminateSubClassesOnColumn("ItemType");
        this.Id(x => x.ItemId, "ItemId");
        this.Map(x => x.FieldA, "FieldA");
    }
}

Then map your abstract subclass like this:

public class SubItemMap: SubclassMap
{
    public SubItemMap()
    {
        this.Map(x => x.FieldB);
    }
}

Then map your concrete subclasses like so:

public class ConcreteItemXMap : SubclassMap
{
    public ConcretItemXMap()
    {
        this.Join("ConcreteItemX", x =>
        {
            x.KeyColumn("ItemID");
            x.Map("FieldC")
        });
    }
}

Hopefully this helps somebody else looking for this type of mapping with fluent.