Hello;
Thank you for your help.

I tried to override PopulateForeignParentKeyField method in our top level sub business class like this.

foreach (string ParentKeyField in _ForeignParentKeyFields) {
base.PopulateKeyField(ParentKeyField, whereIsTheKeyFieldValue);
}

And now, we have got new problem about KeyFields values. How can we get every key fields value?

Best regards.