Question

I have a thesaurus application built on NHibernate. The data model is very straight-forward:

public class Word
{
    public virtual int Id { get; set; }
    public virtual string Text { get; set; }
    public virtual IList<Word> Synonyms { get; set; }
    public virtual IList<Word> Antonyms { get; set; }
}

So each word has a list of synonyms and a list of antonyms. I thought the mapping would be straight-forward as well:

public class WordMapping : ClassMap<Word>
{
    public WordMapping()
    {
        Id(x => x.Id);
        Map(x => x.Text);
        HasMany(x => x.Synonyms).Cascade.AllDeleteOrphan();
        HasMany(x => x.Antonyms).Cascade.AllDeleteOrphan();
    }
}

When I look at the table generated in MS SQL Server 2008, I only see one key column for the two HasMany relations:

Id        int
Text      nvarchar(255)
Word_id   int

I think this is causing some weird things to happen when I insert data. When I get the lists after doing some insertions, both Synonyms and Antonyms contain the same Words, but the Words are just seemingly-arbitrary subsets of what should be in the two lists.

Do I have the problem pegged right? If so, how can I fix it?

Answer 1

I was way off base. I assumed FNH was generating a separate table for the HasMany relationships (it wasn’t). Proper code found here: Fluent NHibernate Self Referencing Many To Many

Specific to my problem, I created two separate tables:

-- Synonyms table --
WordId        int
SynonymId     int

-- Antonyms table --
WordId        int
AntonymId     int

Then in my mapping class:

public class WordMapping : ClassMap<Word>
{
    public WordMapping()
    {
        Id(x => x.Id);
        Map(x => x.Text);
        HasManyToMany(x => x.Synonyms).ParentKeyColumn("WordId")
                                              .ChildKeyColumn("SynonymId")
                                              .Table("Synonyms");
        HasManyToMany(x => x.Antonyms).ParentKeyColumn("WordId")
                                              .ChildKeyColumn("AntonymId")
                                              .Table("Antonyms");
    }
}

That fixes all the issues.