Well, there's the 'Algemene Wet Gelijke Behandeling' (common law for equal treatment), which further specifies the 'whatever other basis', and our criminal law, article 137 contains guidelines on how to penalize discrimination.
It is mostly a catch all for unfair grounds of discimination not specifically mentioned.
The equal in equal cases means that, for example, you cannot pay a different wage to men or women who do the same, or very similar work.
It does not disallow justified discrimination, like only hiring someone to be a doctor who has actually gone to med school (thereby discriminating people who did not go to med school).
Must be noted that the Dutch laws cannot be directly tested to the Constitution once they have been passed. Our Constitution is a guideline for judges and politicians, to use as a basis for passing judgement and making new laws.
It is one of the Senate's tasks to look at new legislation and see if it is in accordance with the Constitution.
And then it is a judge's task to look at the laws and see if jurisprudence is needed in cases where in practical application, new laws have friction with the Constitution.
You cannot go to court saying 'Somebody broke art. 1 of the constitution, I will sue'.
Instead you file discrimination charges, and a judge will look at the appropriate articles in the corresponding field of law (criminal law, administrative law, civil law) to pass judgement.