Setting up Fluent NHibernate one-to-many with cascading deletes using the automapper

Question

Extreme newbie question. I have my database (SQL Server) set up to cascade deletes for my relationships so if you delete a parent entity all the children are deleted as well (ON DELETE CASCADE). I want this to be reflected in my automapped Fluent NHibernate setup. However, when I try to delete a child entity NHibernate is instead attempting to set the relationship key to NULL.

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

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

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

My entities (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; }
}

Here's how the SessionFactory looks:

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 it has to do is delete, but instead it's trying to set a non-nullable foreign key to null. What's going on?

score 2 · Accepted Answer · edited May 23 '17 at 12:03

2

Deletes do not cascade by default in NHibernate. Set cascading on codeGroup.Codes relationship like this:

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

And similarly for other relations that you need to be influenced.

Edited by OP: Just needed that ".Inverse()" at the end. Related to this question: key-many-to-one and key-property association: nhibernate won't DELETE items from set

edited May 23 '17 at 12:03

Community

1
1

answered Oct 25 '11 at 17:46

NOtherDev

9,542
2
36
47

`AllDeleteOrphan()` isn't a member of `Cascade` -- perhaps you mean "`All()`" ? – roufamatic Oct 25 '11 at 18:58
You're right. `AllDeleteOrphan` is for *one-to-many* only, `All` will go here. – NOtherDev Oct 25 '11 at 19:01
Nope, this isn't working -- `An association from the table CodeGroup refers to an unmapped class: System.Collection.Generic.IList``1[[MyNamespace.Code, ...]]` – roufamatic Oct 25 '11 at 19:04
OK, this IS *one-to-many*, so it was correct before, but with different relation mapping. See corrected answer. Sorry for mess. – NOtherDev Oct 25 '11 at 19:17
Same error. Hey, is there any significance to the message "could not delete collection" ? That seems ominous -- it shouldn't be trying to delete a collection, just an entity. – roufamatic Oct 25 '11 at 20:16
I've got it: need to add `.Inverse()` to the end of that `AllDeleteOrphan()` call. See http://stackoverflow.com/questions/1541660/key-many-to-one-and-key-property-association-nhibernate-wont-delete-items-from . – roufamatic Oct 25 '11 at 20:20

score 1 · Answer 2 · answered Oct 26 '11 at 01:42

You might be hitting this issue. Unless you're running 3.2.0Beta2 or later, if you want to cascade deletes you must either:

make the child's FK nullable; or
create a inverse relationship (that is, the child must have a mapped reference to the parent).

As you can see from the ticket this has been longstanding (and much upvoted) issue that has very recently been fixed.

Setting up Fluent NHibernate one-to-many with cascading deletes using the automapper

2 Answers2