Fluent NHibernate: foreign key not null problem

Question

I have the following domain classes:

public class Installation : Entity<Installation>
{        
    public virtual string Name { get; set; }
    public virtual IList<Institution> Institutions { get; set; }

    public Installation()
    {
        Institutions = new List<Institution>();
    }
}
public class Institution : Entity
{
    public virtual string Name { get; set; }
    public virtual string Address { get; set; }
    public virtual string City { get; set; }
    public virtual Installation Installation { get; set; }        
}

I have made the Entity base class according to the following post. I have the following mappings defined:

public class InstitutionMapping : ClassMap<Institution> 
{
    public InstitutionMapping()
    {
        WithTable("Institution");
        Id(i => i.Id).GeneratedBy.Guid();
        Map(i => i.Name).Not.Nullable().WithLengthOf(50);
        Map(i => i.Address).Not.Nullable().WithLengthOf(50);
        Map(i => i.City).Not.Nullable().WithLengthOf(50);
        References(i => i.Installation).ColumnName("InstallationId").Not.Nullable().WithForeignKey();
    }
}
public class InstallationMapping : ClassMap<Installation>
{
    public InstallationMapping()
    {
        WithTable("Installation");
        Id(i => i.Id).GeneratedBy.Guid();
        Map(i => i.Name).Not.Nullable().WithLengthOf(50);
        HasMany<Institution>(i => i.Institutions).KeyColumnNames.Add("InstallationId").Cascade.All();
    }
}

When I run the following code:

Installation installation = TestHelper.CreateAnonymousInstallation();
installation.Institutions.Add(TestHelper.CreateAnonymousInstitution());
installation.Institutions.Add(TestHelper.CreateAnonymousInstitution());
session.Save(installation);

I get the following error:

NHibernate.PropertyValueException: not-null property references a null or transient value.

How to overcome the problem?

Thanks in advance Lukasz Glaz

Answer 1

As I can see your Institution class has reference on Installation class. And this reference is set to not null. When you are creating AnonymousInstitution do you set some Installation for it?

Answer 2

I believe it's inverse=true that is needed.

HasMany<Institution>(i => i.Institutions)
   .KeyColumnNames.Add("InstallationId")
   .Cascade.All()
   .Inverse();

Or of course add a method in the installation class to handle this explicitly.

public class Installation : Entity<Installation>
{        
    public virtual string Name { get; set; }
    public virtual IList<Institution> Institutions { get; set; }

    public Installation()
    {
        Institutions = new List<Institution>();
    }

    public virtual void AddInstitution(Institution entity)
    {
        entity.Installation = this;
        Institutions.Add(entity);
    }
}