He married his fourth wife, Susan, in the vain hope that she would improve his health.

他怀着她能改善自己健康的徒然希望娶了第4个妻子苏珊。

《柯林斯英汉双解大词典》

I knocked loudly in the vain hope that someone might answer.

我敲门敲得很响，希望有人应声，却是徒然。

《牛津词典》

In the (perhaps vain) hope of gaining some calm perspective, let's consult two people who are frequently quoted on housing and mortgage matters.

抱着获得一些冷静看法的希望(或许只是徒劳)，让我们看看在楼市和抵押贷款问题上经常被引用的两位人士的意见。

youdao

"But I hope that the love that people have shown will make you know he didn't live in vain,".

VOA: standard.2009.07.07

Or do we stand with their oppressors, in the vain hope that the latter will treat us better?

CENTERFORSECURITYPOLICY: Freedom��s champions

President Obama's alienating of Israel, Poland, the Czech Republic, Honduras and other allies in the vain hope of currying favor with their foes, and ours.

CENTERFORSECURITYPOLICY: Hold Obama Accountable

Now Malaysia appears intent on following those same models once more, by deferring an inevitable financial crisis in the vain hope that something will turn up.

ECONOMIST: Dead Ostrich Bounce