枉费

They tried in vain to persuade her to go.

极劝她去，但枉费了一番口舌。

The reactionary government tried vainly to take the steam out of the protest movement.

动政府枉费心机地企图削弱这场抗议运动。

Those who protested against the president's decision were actually barking at the moon, since they were in a powerless minority.

由于于软弱无的少数, 总统的决定实际上枉费唇舌。