Fluent nHibernate mapping problem

Question

I have these tables/classes (example):

table FirstTable (
    Id INTEGER NOT NULL DEFAULT AUTOINCREMENT, 
    Name VARCHAR(100) NOT NULL,
    Document VARCHAR(20) NOT NULL
)

table SecondTable (
    Id INTEGER NOT NULL,
    Something VARCHAR(100) NULL,
    FOREIGN KEY (Id) REFERENCES FirstTable (Id)
)

public class FirstClass {
    public string Name { get; set; }
    public string Document { get; set; }
    public SecondClass SecondClass { get; set; }
}

public class SecondClass {
    public string Something { get; set; }
    public FirstClass FirstClass { get; set; }
}

The mapping is:

public class FirstClassMap : ClassMap<FirtsClass> {
    Table("FirstTable");
    Id(x => x.Id).GeneratedBy.Identity();
    Map(x => x.Name);
    Map(x => x.Document);
    References(x => x.SecondClass, "Id").ForeignKey();
}

public class SecondClassMap : ClassMap<SecondClass> {
    Table("SecondTable");
    Id(x => x.Id).GeneratedBy.Foreign("FirstClass");
    Max(x => x.Something);
    HasOne(x => x.FirstClass).PropertyRef(x => x.SecondClass).Cascade.SaveUpdate();
}

FirstClass can have (0,1) SecondClass, and SecondClass can have (1,1) FirstClass.

The bellow code return the error "attempted to assign id from null one-to-one property: SecondClass"

var test = new SecondClass();
test.FirstClass = new FirstClass();

test.Something = "New test";
test.FirstClass.Name = "My name";
test.FirstClass.Document = "My document";
// ... commands to save.

Does it work when you invert the instantiation? first instantiate FirstClass and then assign a new SecondClass to it. — Variant
– Variant, Commented Jun 6, 2011 at 22:01

Variant · Accepted Answer · 2011-06-07 06:53:14Z

2

It seems like NH is trying to save SecondClass first and fails to grab a generated ID from the not yet saved FirstClass.

Try to move the .Cascade.SaveUpdate() to the References declaration in FirstClassMap and call the save command on FirstClass.

answered Jun 7, 2011 at 6:53

Variant

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1 Comment

Cesar Over a year ago

This works, tks, I save the FirstClass with SecondClass null, after I set SecondClass in FirstClass and save. Tks. +1

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