Fluent NHibernate inheritance mapping

Question

In my hierarchy of animals

Base one:

public class AnimalMap : ClassMap<Animal>
{
    public AnimalMap()
    {
      Schema("dbo");
      Table("Animals");   

      Id(x => x.Id).Column("ID").GeneratedBy.Identity();
      Map(x => x.FoodClassification).Column("FoodClassification");
      Map(x => x.BirthDate).Column("BirthDate");
      Map(x => x.Family).Column("Family");

      DiscriminateSubClassesOnColumn("ClassType").Not.Nullable();    
    }
}

One subclass:

public class DogMap : SubclassMap<Dog>
{
    public DogMap()
    {
          DiscriminatorValue(@"Dog");
          Map(x => x.Field).Column("Field");
    }
}

So the question is:

Where column "ClassType" != Dog , Animal should be object type, like base one. Each one who has no mapping class should have base(super) one.

How to make it works?

I don't think it's possible, if you had a class of type Giraffe : Animal, how would the column value be persisted if you never specified a discriminator value for giraffe. — Matthew
– Matthew, Commented Dec 5, 2013 at 15:44
but what should to do if i don't need classification for everyone who is not a dog? i mean each?, even giraffe, should be an animal but not a giraffe — Roar
– Roar, Commented Dec 5, 2013 at 16:07
some other word like 'animal' but not dog... or null or empty string. whatever, but they should be Animal class type — Roar
– Roar, Commented Dec 8, 2013 at 17:48
Try to make a common abstract base type (like BaseAnimal), and have both Animal and Dog derive from it. Then you would set-up 2 subclass mappings. — Matthew
– Matthew, Commented Dec 8, 2013 at 23:40

Firo · Accepted Answer · 2013-12-10 12:21:23Z

1

important: only do this to support legacy schemas and animal is readonly

public class SomeAnimal : Animal
{

}

public class AnimalMap : ClassMap<Animal>
{
    public AnimalMap()
    {
      Schema("dbo");
      Table("Animals");   

      Id(x => x.Id).Column("ID").GeneratedBy.Identity();
      Map(x => x.FoodClassification).Column("FoodClassification");
      Map(x => x.BirthDate).Column("BirthDate");
      Map(x => x.Family).Column("Family");

      DiscriminateSubClassesOnColumn().Formula("IIF(classtype = 'dog', 'dog', 'someAnimal')");
    }
}

public class SomeAnimalMap : SubclassMap<SomeAnimal>
{
    public SomeAnimalMap()
    {
          ReadOnly();

          DiscriminatorValue("someAnimal");
          Map(x => x.ClassType).Column("classtype");
    }
}

answered Dec 10, 2013 at 12:21

Firo

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4 Comments

Roar Over a year ago

see the solution, but question is how to avoid this one?

Firo Over a year ago

Avoid specifying all subclass values in the Formula or the additional class SomeAnimal?

Roar Over a year ago

additional class SomeAnimal

Firo Over a year ago

you can with DiscriminateSubClassesOnColumn("", "someAnimal").Formula(...);

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