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Direction of Many-to-many mapping

Original Post

Marta

30 Apr, 2010 01:57 PM via web

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Hi,
How are you?
I have recently discovered Fluent NHibernate, and there is something that I don't undestand about the way Automapping resolve many-to-many relationships.
Initially I thougth the mapping would be bidirectional, but then I discover that is unidirectional and I don't know how to specify the
direction.
Is there any way to do it?

Thank you very much,
Marta.

1. 2 Posted by Devon Lazarus on 05 May, 2010 02:46 PM

   

   The mapping is only bi-directional if you specify the collection in another entity.

   "Setting the direction" is kind of a misnomer in my opinion. You're not really setting the direction, you're telling NH which side of the collection is responsible for cascading the save/update/delete call.

   If you want to control this, you would use .Inverse() on the side of the collection you do not want to cascade from:

   public class EntityOne {
       ...
       HasManyToMany<MyEntity>(x => x.Entities)
           .AsBag()
           .Inverse();
   }
   
   public class EntityTwo {
       ...
       HasManyToMany<MyEntity>(x => x.Entities)
           .AsBag();
   }
   

   Using this mapping, MyEntity objects added to EntityOne would not be saved in the database unless they were also added to the EntityTwo.Entities collection.

   hth,

   -devon

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2. James Gregory resolved this discussion on 16 May, 2010 05:24 PM.

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