I have a Class A:

public class ClassA
{
      public int ID {get; private set;}
      public string Code {get; private set;}
      public ClassB B {get; private set;}
      public IList<ClassB> ListB {get; private set;}

}

And a ClassB:

public class ClassB
{
      public int ID {get; private set;}
      public string Code {get; private set;}
      public ClassA A {get; private set;}
      //some other attributes...
}

And the Mappings:

public ClassAMap()
{
    Table("ClassA");

    Id(classA => classA .ID, "ID").GeneratedBy.Identity();
    Map(classA  => classA.Code, "Code").Unique().Not.Nullable();
   //HERE IS THE PROBLEM: --------
    References(classA  => classA.B,"IDClassB").Cascade.SaveUpdate(); 
   //-----
    HasMany(classA  => classA.ListB).Table("ClassB").KeyColumn("IDClassA").AsBag().Not.LazyLoad().Inverse().Cascade.AllDeleteOrphan();
}

ClassB Mappings:

public ClassBMap()
{
    Table("ClassB");
    Id(classB => classB.ID).GeneratedBy.Identity();
    References(classB => classB.A, "IDClassA").ForeignKey("ID").Cascade.SaveUpdate();

}

The mappings for ListB in classA worked ok, because at first the was only ListB property and not B, when i had to map B i tried this:

References(classA  => classA.B,"IDClassB");

The mapping test failed because B wasn't saved, so i did this:

References(classA  => classA.B,"IDClassB").Cascade.SaveUpdate();

This time B was saved, but by saving B, classA was inserted two times, by A.B and by B.A.

How can i solve this problem? Why does it work for the ListB property and not for the B property? Thanks