I know that it's not advised to disclose your present salary when negotiating with a prospective employer.
However I am in the situation where I work for company A via agency B, and company A has precise rules on the salaries to be paid to external employers like me. This means that they, knowing the tariff they pay to the agency, also know my salary, at least the range if not even to the cent.
Now company A wants to hire me directly for the same position where I am now. Besides giving an excellent performance before the switch, is there any other way I can negotiate a salary rise?