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Configure Fluent NHibernate one-to-many with cascading deletes using automapper

Extreme newbie question. I have my database (SQL Server) configured for cascading deletes for my relationships, so if you delete the parent object, all children are also deleted ( ON DELETE CASCADE ). I want this to reflect on my unattended installation of Fluent NHibernate. However, when I try to delete a child, NHibernate instead tries to set the relation key to NULL.

The database is super simple: ( -- for "one", -< for "many")

 User ---< UserCode >--- Code >--- CodeGroup

When I delete CodeGroup , it deletes the cascade to Code and UserCode . When I delete the code, it should just cascade to UserCode , but leave the CodeGroup untouched.

My objects (properties removed for clarity):

 public class User { public virtual IList<Code> FoundCodes { get; private set; } } public class Code { public virtual IList<User> UsersWithCode { get; private set; } public virtual CodeGroup CodeGroup { get; set; } } public class CodeGroup { public virtual IList<Code> Codes { get; private set; } }

This is what SessionFactory looks like:

 var _sessionFactory = Fluently.Configure() .Database(FluentNHibernate.Cfg.Db.MsSqlConfiguration.MsSql2005.ConnectionString(c => c.FromConnectionStringWithKey("db")).ShowSql()) .Cache(csb => csb.UseQueryCache()) .Mappings(m => m.AutoMappings.Add( AutoMap.AssemblyOf<Code>(new AutomappingConfiguration()) .Override<User>(map => map.HasManyToMany(u => u.FoundCodes).Table("UserCode")) .Override<Code>(map => map.HasManyToMany(c => c.UsersWithCode).Inverse().Table("UserCode")) .Conventions.Add(new CustomForeignKeyConvention()))) .BuildSessionFactory())

But when I do this:

 using (var tx = _db.BeginTransaction()) { var codeGroup = _db.Load<CodeGroup>(id); _db.Delete(codeGroup); tx.Commit(); }

I get this:

 could not delete collection: [MidnightRoseRace.Data.Entities.CodeGroup.Codes#8] [SQL: UPDATE [Code] SET CodeGroupId = null WHERE CodeGroupId = @p0] Cannot insert the value NULL into column 'CodeGroupId', table 'MyNamespace.dbo.Code'; column does not allow nulls. UPDATE fails. The statement has been terminated.

All he needs to do is delete, but instead he tries to set the invalid foreign key to null. What's happening?

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2 answers

By default, cascades are removed in NHibernate. codeGroup.Codes relation as follows:

 AutoMap.AssemblyOf<Code>(new AutomappingConfiguration()) // existing overrides .Override<CodeGroup>( map => map.HasMany(c => c.Codes).Cascade.AllDeleteOrphan().Inverse())

And similarly for other relationships that need to be influenced.

Edited by OP: Just need to have ".Inverse ()" at the end. Related to this question: key-many-to-one and key-property association: nhibernate will not remove items from a set

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You can push this problem . If you are not using 3.2.0Beta2 or later, if you want to perform cascading deletes, you must either:

  • make child FK null; or
  • create feedback (that is, the child must have a matching link to the parent).

As you can see from the ticket, this is a long-standing (and many times) problem, which has recently been fixed.

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