C# – Hibernate/NHibernate : how to persist subclass as instance of superclass

chibernatenhibernatesubclass

I have two classes I would like to persist via NHibernate:
– Cat, which has a name and an Id,
– Kitten, which is a subclass of Cat (no extra public properties).

For stupid reasons, I would like to know if it is possible to map Cat only? So that when I persist Kitten, it is saved as a Cat and when I reload it, it is loaded as a Cat.

Additional constraints :
– When trying, NHibernate crashed because it did not know Kitten.
– However I do not want to add a discriminator value, as I do not want Hibernate to instantiate the Kitten subclass.

Thank you very much!

EDIT :
I forgot to write that using explicit ISession.Save("Cat", kitten) works. My problem occurs during a cascading save.

Best Answer

Old question, I guess I would have to use interfaces instead.

Related Solutions

C# – How to create a new object instance from a Type

The Activator class within the root System namespace is pretty powerful.

There are a lot of overloads for passing parameters to the constructor and such. Check out the documentation at:

http://msdn.microsoft.com/en-us/library/system.activator.createinstance.aspx

or (new path)

https://docs.microsoft.com/en-us/dotnet/api/system.activator.createinstance

Here are some simple examples:

ObjectType instance = (ObjectType)Activator.CreateInstance(objectType);

ObjectType instance = (ObjectType)Activator.CreateInstance("MyAssembly","MyNamespace.ObjectType");

C# – Fluent NHibernate entity HasMany collections of different subclass types

You mapping looks odd, in particular I think it should look more like this

DiscriminateSubClassesOnColumn<string>("Type")
               .SubClass<EntityA>("A", m => { })
               .SubClass<EntityB>("B", m => { });

Having said that it seems that method is depreciated and you should instead define the following (taken from Automapping Subclasses:

public class ParentMap : ClassMap<Parent>
{
  public ParentMap()
  {
    Id(x => x.Id);
    Map(x => x.Name);

    DiscriminateSubClassesOnColumn("type");
  }
}

public class ChildMap : SubclassMap<Child>
{
  public ChildMap()
  {
    Map(x => x.AnotherProperty);
  }
}

Not sure this will fix it though, I am yet to encounter your scenario.

Edit: The issue is also raised here, sounding more like a bug to me

Best Answer

Related Solutions

C# – How to create a new object instance from a Type

C# – Fluent NHibernate entity HasMany collections of different subclass types

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