Fluent NHibernate: Map property without foreign key?

Question

I have these two classes:

public class Parent
{
    public virtual string Name { get; set; }
    public virtual string Family_id { get; set; }
}

public class Children
{
    public virtual string Name { get; set; }
    public virtual DateTime BirthDate { get; set; }
    public virtual string Family_id { get; set; }
}

When I fetch a parent, I also want to fetch the oldest (ordered by BirthDate) children that has the same Family_id as the parent.

There is no foreign key between the parent and the children in the database.

(I do not want to use two different repositories, I want the functionality in the mappings)

Is property-ref something I can use?

score 2 · Answer 1 · answered May 24 '11 at 16:02

One strategy would be to force an Eager Load on a Children collection and create another property to get the oldest child.

Property-Ref is used to join to another table using a column which is not the primary key.

public class Parent
{
    public virtual int Id {get; set;}
    public virtual string Name { get; set; }
    public virtual string Family_id { get; set; }
    public virtual Children OldestChild {
     get {
          return Children.OrderBy(x=>x.BirthDate).FirstOrDefault();
     }}
    public virtual IList<Children> Children {get; set;}
}

public class ParentMap : ClassMap<Parent>{
    public ParentMap(){
        Id(x=>x.Id);
        Map(x=>x.Name);
        HasMany(x=>x.Children).PropertyRef("Family_id").Fetch.Join();
    }
}

Another possibility would be to add a column to the Parent table (OldestChild_FK) and then join in that row from the Children table.

Thanks for your suggestion, Mark. Is it possible to do the OrderBy functionality in the mappings? — Awesome, May 25 '11 at 07:41
You can use the `.AsSet` method on the mapping to give you an orderedSet opposed to an IList. So yes there are options to order your Children by BirthDate and have the appear in the `Children` in the correct order. — Mark Perry, Sep 02 '11 at 11:03

score 1 · Answer 2 · edited May 23 '17 at 12:12

1

I think what you want to do is create a property on the Parent called OldestChild or a list of Oldest Children and ignore that property and write some custom query (HQL or SQL) to return the results you want.

Here is a thread on ignoring properties in FluentNhibernate.

edited May 23 '17 at 12:12

Community

1
1

answered May 24 '11 at 07:51

Pieter Germishuys

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Do I really need to ignore the property if auto-mapping isn't used? – Awesome May 24 '11 at 07:55
If automapping isn't used, you don't need to ignore the property. – Pieter Germishuys May 24 '11 at 08:09

Fluent NHibernate: Map property without foreign key?

2 Answers2