How to do a fluent nhibernate one to one mapping?

Question

How do I do this I am trying to make a one to one mapping.

public class Setting
{
    public virtual Guid StudentId { get; set; }
    public virtual DateFilt         


        

Answer 1

There are two basic ways how to map bidirectional one-to-one association in NH. Let's say the classes look like this:

public class Setting
{
    public virtual Guid Id { get; set; }
    public virtual Student Student { get; set; }
}

public class Student
{
    public virtual Guid Id { get; set; }
    public virtual Setting Setting { get; set; }
}

Setting class is a master in the association ("aggregate root"). It is quite unusual but it depends on problem domain...

Primary key association

public SettingMap()
{
    Id(x => x.Id).GeneratedBy.Guid();
    HasOne(x => x.Student).Cascade.All();
}

public StudentMap()
{
    Id(x => x.Id).GeneratedBy.Foreign("Setting");
    HasOne(x => x.Setting).Constrained();
}

and a new setting instance should be stored:

        var setting = new Setting();

        setting.Student = new Student();
        setting.Student.Name = "student1";
        setting.Student.Setting = setting;
        setting.Name = "setting1";

        session.Save(setting);

Foreign key association

public SettingMap()
{
    Id(x => x.Id).GeneratedBy.Guid();
    References(x => x.Student).Unique().Cascade.All();
}

public StudentMap()
{
    Id(x => x.Id).GeneratedBy.Guid();
    HasOne(x => x.Setting).Cascade.All().PropertyRef("Student");
}

Primary key association is close to your solution. Primary key association should be used only when you are absolutely sure that the association will be always one-to-one. Note that AllDeleteOrphan cascade is not supported for one-to-one in NH.

EDIT: For more details see:

http://fabiomaulo.blogspot.com/2010/03/conform-mapping-one-to-one.html

http://ayende.com/blog/3960/nhibernate-mapping-one-to-one