c# - 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 DateFilters TaskFilterOption { get; set; }
    public virtual string TimeZoneId { get; set; }
    public virtual string TimeZoneName { get; set; }
    public virtual DateTime EndOfTerm { get; set; }
    public virtual Student Student { get; set; }

}

// class map

 public SettingMap()
        {
           /// Id(Reveal.Member<Setting>("StudentId")).GeneratedBy.Foreign("StudentId");
            //Id(x => x.StudentId);
            Map(x => x.TaskFilterOption).Default(DateFilters.All.ToString()).NvarcharWithMaxSize().Not.Nullable();
            Map(x => x.TimeZoneId).NvarcharWithMaxSize().Not.Nullable();
            Map(x => x.TimeZoneName).NvarcharWithMaxSize().Not.Nullable();
            Map(x => x.EndOfTerm).Default("5/21/2011").Not.Nullable();
            HasOne(x => x.Student);
        }

// student map

public class StudentMap : ClassMap<Student>
    {
        public StudentMap()
        {
            Id(x => x.StudentId);
            HasOne(x => x.Setting).Cascade.All();

        }
    }

  public class Student
    {
        public virtual Guid StudentId { get; private set; }
        public virtual Setting Setting { get; set; }
    }

Now every time I try to create a settings object and save it to the database it crashes.

   Setting setting = new Setting
                                          {
                                              TimeZoneId = viewModel.SelectedTimeZone, 
                                              TimeZoneName = info.DisplayName, 
                                              EndOfTerm =  DateTime.UtcNow.AddDays(-1),
                                              Student = student
                                          };

The INSERT statement conflicted with the FOREIGN KEY constraint "FK_Settings_Students". The conflict occurred in database "Database", table "dbo.Students", column 'StudentId'.
The statement has been terminated.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Data.SqlClient.SqlException: The INSERT statement conflicted with the FOREIGN KEY constraint "FK_Settings_Students". The conflict occurred in database "Database", table "dbo.Students", column 'StudentId'.
The statement has been terminated.

What am I missing?

Edit

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

public class SettingMap : ClassMap<Setting>
{
    public SettingMap()
    {
        Id(x => x.StudentId).GeneratedBy.Guid();
        Map(x => x.TaskFilterOption).Default(DateFilters.All.ToString()).NvarcharWithMaxSize().Not.Nullable();
        Map(x => x.TimeZoneId).NvarcharWithMaxSize().Not.Nullable();
        Map(x => x.TimeZoneName).NvarcharWithMaxSize().Not.Nullable();
        Map(x => x.EndOfTerm).Default("5/21/2011").Not.Nullable();
        References(x => x.Student).Unique();
    }
}

// try 1

      Setting setting = new Setting
                                          {
                                              TimeZoneId = viewModel.SelectedTimeZone, 
                                              TimeZoneName = info.DisplayName, 
                                              EndOfTerm =  DateTime.UtcNow.AddDays(-1),
                                              Student = student
                                          };
     studentRepo.SaveSettings(setting);
     studentRepo.Commit();

// try 2

  Setting setting = new Setting
                                          {
                                              TimeZoneId = viewModel.SelectedTimeZone, 
                                              TimeZoneName = info.DisplayName, 
                                              EndOfTerm =  DateTime.UtcNow.AddDays(-1),
                                              Student = student
                                          };

student.Setting = setting
studentRepo.CreateStudent(student);
studentRepo.Commit();

I get these error for both ways

Invalid index 5 for this SqlParameterCollection with Count=5. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.IndexOutOfRangeException: Invalid index 5 for this SqlParameterCollection with Count=5.

Source Error:

Line 76:             using (ITransaction transaction = session.BeginTransaction()) Line 77:   { Line 78:                 transaction.Commit(); Line 79:         } Line 80:         }

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