Map foreign key as well as reference in NHibernate without creating extra column

Question

I want to map both the foreign key as a POCO property and the navigation property. IE in the example here , the answer substitutes the foreign key

 public virtual int SongArtistID { get; set; }

I want to keep that key in the mapping. I have tried so far:

Map(x => x.ParentID);
References(x => x.Parent).Column("ParentID");

Map(x => x.ParentID);
References(x => x.Parent, "ParentID");

and many other combinations using the fluent mapper but I can't get it working. The problem is that the References() directive always creates an extra column.

score 4 · Answer 1 · answered Sep 16 '12 at 02:30

4

You don't map the same relationship twice in NHibernate.

It's just:

References(x => x.Parent, "ParentID")

And then you use this to get the FK value:

var parentId = obj.Parent.Id;

Or this to assign it:

obj.Parent = session.Load<TheClassOfTheParent>(parentId);

And none of those statements will result in a db call.

answered Sep 16 '12 at 02:30

Diego Mijelshon

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I don't want to map a relationship twice, I just want to access the property as a simple (for example int) property without any knowledge of ORM, session, etc, just data model – Mihalis Bagos Sep 16 '12 at 14:05
Well, it won't work. NHibernate is oriented towards working with an object model based on relationships, not a DB model based on foreign keys. – Diego Mijelshon Sep 16 '12 at 14:48
1

Actually, it works, problem wasnt in `Reference()` see my reply – Mihalis Bagos Sep 17 '12 at 09:16
Thank you for the reply and attention however! – Mihalis Bagos Sep 17 '12 at 09:23
I would disagree with @DiegoMijelshon, see my answer here http://stackoverflow.com/a/37436232/173073 – Dzmitry Lahoda May 25 '16 at 11:49

score 3 · Answer 2 · answered Sep 17 '12 at 09:20

As it turns out, mapping the way I showed was perfectly fine. The problem with the extra field was created by the other side of the relationship. What I had was:

class ParentMap

        HasMany(x => x.Children)
            .Inverse()
            .Cascade.All();

class ChildMap

        Map(x => x.ParentID);
        References(x => x.Parent).Column("ParentID");

I had to specify the column on the HasMany() of the parent instead of actually on the Reference() of the child, like so:

class ParentMap

        HasMany(x => x.Children)
            .KeyColumn("ParentID") // Problem without this!
            .Inverse()
            .Cascade.All();

Map foreign key as well as reference in NHibernate without creating extra column

2 Answers2