Examples

if you had asked him he would have done it

如果你问过他的话，他早就会做了

Really，you shouldn't have done it.

真的吗，你不应该做那事。

to have seen/done it all

全都看了/做了

If you want it done in half the time , you've got to have twice as many people.

如果你想用一时间完成它，你就要双倍数量的人。

没有搞过这种工作，就不知道其中的甘苦。

You don't know how difficult the job is, unless you have done it yourself.

我若是他，决不会那么办。

If I were him, I wouldn't have done it that way.

涓埃小事，就不用谢了，何况这是我应该做的。

There is no need to be thankful for such an insignificant thing. Besides, it was what I should have done.

“早知今日何必当初呀！”他喟叹道。

"If I had known that things would turn out this way, I would not have done it," he sighed regretfully.

到现在还没开始，你想明天交白卷啊？

You still haven't even started. You won't have done it by tomorrow, will you?