fluent nhibernate mapping with not null foreign key (HasMany)

3
votes

I have the following mapping in nhibernate. When I call Session.Merge(myparent) I get the an error on the insert indicating that NULL cannot be inserted into the foreign key (ParentItemId) column.

How can I adjust the mapping so that the parent key is inserted on insert. If I make the foreign key nullable this mapping works, but two separate statements are issued to the database.

This relationship is a one to many without a reference back to the parent on the child class.

  • The child class has no parent property.
  • The child is dependent on the parent. 
    HasMany(map => map.Children).Table("ChilrenTable")
   .KeyColumn("ParentItemId") // this is not nullable.
   .Cascade
   .AllDeleteOrphan();

    example update

    // entity here is the parent instance, which contains the list
// of children.
using (var tx = Session.BeginTransaction())
{
    entity = Session.Merge(entity); // this line causes the problem.
    Session.SaveOrUpdate(entity);
    Session.Flush();
    tx.Commit();
    return entity;
}
    • 1
    c#nhibernatefluent-nhibernate

    1 Answers

    3
    votes

    Inverse Attribute in NHibernate

    HasMany(map => map.Children).Table("ChilrenTable")
   .KeyColumn("ParentId") // this is not nullable.
   .Inverse()  // <--- This is the key here
   .Cascade
   .AllDeleteOrphan();