The third benefit of the Crossbow Expert feat says (PHB, p. 165):
When you use the Attack action and attack with a one-handed weapon, you can use a bonus action to attack with a hand crossbow you are holding.
I am aware that in general, the order of action/bonus action is irrelevant. However, does the wording of Crossbow Expert's third benefit mean that it requires taking the Attack action before the bonus action?
Compare/contrast that wording with that of:
the third benefit of the monk's Martial Arts feature:
When you use the Attack action with an unarmed strike or a monk weapon
on your turn, you can make one unarmed strike as a bonus action. For
example, if you take the Attack action and attack with a quarterstaff,
you can also make an unarmed strike as a bonus action, assuming you
haven't already taken a bonus action this turn.
the monk's Flurry of Blows option for the Ki feature:
Immediately after you take the Attack action on your turn, you can
spend 1 ki point to make two unarmed strikes as a bonus action.
and the Shield Master feat (PHB, p. 170):
If you take the Attack action on your turn, you can use a bonus action
to try to shove a creature within 5 feet of you with your shield.