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How to map a list of an interface to a concrete class

Asbjørn Ulsberg

25 Oct, 2010 11:11 AM via web

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I'd like to map a list of an interface This is my object:

public class Foo
{
  public virtual IList<IBar> Bars { get; protected set; }
}

I have several implementations of IBar in my domain model. How do I specify which IBar implementation Foo is using with Fluent NHibernate? I'm using auto mapping and would love if there was a solution with overrides.

I feel like there's a missing Class() method somewhere, but I don't know how to map this with NHibernate, so I'm not sure what I want to do is even possible.

1. 2 Posted by Asbjørn Ulsberg on 25 Oct, 2010 12:22 PM

   

   I can add that in the opposite direction of the many-to-one relationship, I have the following:
   

   public class Bar : IBar
   {
       public virtual IFoo Foo { get; protected set }
   }

   And I map this with the following override:
   

   public class BarMap : IAutoMappingOverride<Bar>
   {
       public void Override(AutoMapping<Bar> mapping)
       {
           mapping.References(x => x.Foo)
                  .Class<Foo>();
       }
   }

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2. 3 Posted by Asbjørn Ulsberg on 25 Oct, 2010 04:21 PM

   

   In NHibernate, this seems to be the way to solve it:

   <class name="Foo">
       <bag name="Bars">
           <one-to-many class="Bar" />
       </bag>
   </class>

   However, I find no way to modify <one-to-many class="" /> with FNH, at least not with IAutoMappingOverride. Is there another way to access the @class attribute so I can set it to Bar instad of IBar?

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3. Support Staff 4 Posted by James Gregory on 26 Oct, 2010 12:20 PM

   

   Looks like that's not exposed through either the ClassMap API, or the IAutoMappingOverrides. That's a bummer.

   I think the only option you have (apart from using HBMs) is to create an IHasManyConvention and modify the Relationship property.

   public class BarsConvention : IHasManyConvention, IHasManyConventionAcceptance
   {
     public void Accept(IAcceptanceCriteria<IOneToManyCollectionInspector> criteria)
     {
       criteria.Expect(x => x.Relationship.Class == typeof(IBar));
     }
   
     public void Apply(IOneToManyCollectionInstance instance)
     {
       instance.Relationship.CustomClass<Bar>();
     }
   }

   That might not be perfect, as I don't have a compiler to hand, but it should be close enough.

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