Hmmm thats why I couldn't explain some of its behaviour ;-)
there is propably a very simple explanation for all of this, and there is....
IPredicateExpression filter =
new PredicateExpression(TblPermissionsFields.IdOperator == OperatorID);
TblPermissionsFields.IdOperator is an int
and OperatorID is a long
after changing IdOperator to int, it works like a charm.
so we can all go to sleep now |-)
tanx for al the quick replies !!!