Issue in loading children eagerly

Question

I'm using NHibernate with FluentNH.

Here are the four classes.

FormType

  public class FormType
  {
    public virtual int Id
    { get; set; }

    public virtual string Name
    { get; set; }

    public virtual IList<KeyCompetency> KeyCompetencies 
    { get; set; }
  }

KeyCompetency

  public class KeyCompetency
  {
    public virtual int Id
    { get; set; }

    public virtual string Name
    { get; set; }

    public virtual FormType FormType
    { get; set; }

    public virtual IList<SubCompetency> SubCompetencies 
    { get; set; }
  }

SubCompetency

  public class SubCompetency
  {
    public virtual int Id
    { get; set; }

    public virtual string Name
    { get; set; }    


    public virtual KeyCompetency KeyCompetency
    { get; set; }

    public virtual IList<Ability> Abilities 
    { get; set; }
  }

Ability

  public class Ability
  {
    public virtual int Id
    { get; set; }

    public virtual string Description
    { get; set; }

    public virtual SubCompetency SubCompetency
    { get; set; }
  }

I'm trying to load a formtype based on id.

using (var session = DataContext.OpenSession())
{
    return session.Query<FormType>()
                  .Where(x => x.Id == 1)
                  .FetchMany(x => x.KeyCompetencies)
                  .ThenFetchMany(x => x.SubCompetencies)
                  .ThenFetchMany(x => x.Abilities)
                  .ToList().FirstOrDefault();
}

I'm getting duplicate records for key-competencies, sub-competencies.

Answer 1

Map the collections as Set to avoid this problem. See the answer to this question . Also, since you're selecting by identity it's better to use .SingleOrDefault instead of FirstOrDefault .