Question

I have the classes Foo and Bar:

public class Foo
{
  public int Id {get;set;}
  public IEnumerable<Bar> Bars {get;private set;}
}

public class Bar
{
  public int Id {get;set;}
  public string Type {get;set;}
  public string Description {get;set;}
}

These two classes map to tables in the database in a predictable ‘Bar has foreign key to Foo‘ kind of way. (I can provide the FluentNHibernate mappings if required).

I would like to write a linq query that does the equivalent of this:

SELECT FOOS.*, (SELECT Description FROM BARS WHERE BAR.FOOID = FOO.ID AND BAR.TYPE = 'Irish')
FROM FOOS
WHERE FOO.ID = 1

How would I do this?

And yes, I’m aware that the query will break if the Foo has more than one Irish Bar (although I could use TOP 1 type syntax to protect it). And yes, I mean to use a subquery rather than a join.

EDIT:

This is what I’m trying so far:

var foosWithIrishBarDescription = FooRepository.All.Where(x => x.Id == 1).Select(x=> new {FooId = x.Id, IrishBarDescription = x.Bars.Where(y => y.Type == "Irish").Select(y => y.Description)});

But I get the error ‘The method ‘Select’ is not implemented.’ Can this not be achieved in Linq to NHibernate? (I’m using 2.1).

Answer 1

I assume your IEnumerable is actually a property called “Bars”:

var foos = dbContext.FOOS.Where(f => f.ID == 1);
var foobar = foos.Select(f => new {f, f.Bars.FirstOrDefault(b => b.TYPE == "Irish")});