此前我从未见过这种情况。
cǐ qián wǒ cóngwèi jiànguò zhèzhǒng qíngkuàng 。
I had never seen such a situation before.
他此前已经完成了所有的准备工作。
tā cǐ qián yǐjīng wánchéng le suǒyǒu de zhǔnbèi gōngzuò 。
He had completed all the preparations before.
此前我们讨论过这个问题。
cǐ qián wǒmen tǎolùn guò zhègè wèntí 。
We had discussed this issue before.