forget doing sth.的意思是“忘记做过某事（事情已做）”，表示已经做那件事，只是忘记了曾经做过。
forget doing sth.使用例句
I forgot borrowing a book from you.
我忘记曾经向你借过书这件事。
I just forgot fetching the file.
我忘了已经拿了那份文件了。
I"ll never forget finding that rare old coin in my gardon.
我永远不会忘记在我花园里找到的那枚稀罕的古币。
Mary will never forget seeing the exciting film.
玛丽永远不会忘记看了那部激动人心的电影。
I forgot writing to him,so I wrote again.
我忘了给他写过信，所以我又写了一封信。
He forgot turning the light off.
他不记得他关了灯了
I forgot writing a letter to him.
我忘了给他写过信。
I forgoting closing the window!
我忘记我已关了窗。
