Solve in that way, please confirm is correct
function TDABaseField.GetAsBlob: TBlobData;
begin
{$IFDEF Delphi2009UP}
Result := GetAsBytes;
{$ELSE}
{$IFDEF FPC}
Result := GetAsBytes;
{$ELSE}
Result := AnsiBytesToString(GetAsBytes);
{$ENDIF}
{$ENDIF}
end;