Multiple-step operation generated errors

Napisao sam nesto ovako koriste ADO:

adodsOs->CommandText="
SELECT OID,OCode, OName, OCode + ' ' + OName AS OValue

FROM Basic_Os
WHERE IsActive=1
ORDER BY OCode";

adodsOs->First();
while (!adodsOs->Eof) {
adodsOs->FieldByName(OValue)->ReadOnly = false;
adodsOs->Edit();
adodsOs->FieldValues[OValue] =
Transform(adodsOs->FieldByName(OValue)->AsString);
adodsOs->Post();
adodsOs->Next();
}

i dobijam gresku Multiple-step operation generated errors.

Posto pravim neku univerzakniju funkciju pretpostavljam da se to desi jer negde tip nije string.

Kako bih napisao:

adodsOs->FieldValues[OValue] =
Transform(adodsOs->FieldByName(OValue)->AsString);

ali da koristim nesto univerzalno a ne AsString?