It is so long since I have seen him!

我很久没见到他了！

youdao

I have seen him before.

我以前曾经见到过他。

《新英汉大辞典》

I have seen him once in London.

我在伦敦见过他一次。

youdao

And I believe him. Why,I have seen him set Dan'l Webster down here on this floor--Dan'l Webster was the name of the frog and sing out, "Flies,Dan'l,flies!"

VOA: special.2009.08.29

The thing that we have seen him doing is charging more, but I guess we've got to allow that.

而我们看到的是报纸涨价,但是我想必接受这些

耶鲁公开课 - 金融市场课程节选

The people I live with have seen him around the campus,

跟我一起住的同学在校园见过他，

耶鲁的著名人士 - SpeakingMax英语口语达人

"I have seen him play, but I haven't seen the actual whole game, " said Triche, who said he gets called Howard on occasion.

WSJ: 'The Shot' is still hot topic 26 years later

"I have seen him as a great hero in military uniform and I have seen him as a great hero in peace, " said former President Jimmy Carter.

CNN: Rabin seen as 'a great hero'

He came down for breakfast in a great mood, happily chatting on any number of subjects and appeared as relaxed as I have seen him at any point this week.

BBC: man Robin Chipperfield on Froch-Watch