Solved it.
I changed the sql code of the update query from:
UpdateCommand="UPDATE [Programma] SET [Datum] = ?, [Tijd] = ?, [TeamThuis] = ?, [TeamUit] = ?, [DoelpuntenThuis] = ?, [DoelpuntenUit] = ?, [Opmerkingen] = ?, [ZichtbaarProgramma] = ?, [Oefenwedstrijd] = ? WHERE [ProgrammaID] = ? AND...