forget to do 和forget doing 的区别

forget to do 忘记要去做某事. (未做)
forget doing 忘记做过某事. (已做)
The light in the office is stil on. He forgot to turn it off.
办公室的灯还在亮着,它忘记关了.(没有做关灯的动作)
He forgot turning the light off.
他忘记他已经关了灯了. ( 已做过关灯的动作)
Don't forget to come tomorrow.
别忘了明天来. (to come动作未做)
典型例题
---- The light in the office is still on.
---- Oh,I forgot___.
A. turning it off B. turn it off C. to turn it off D. having turned it off
答案：C.由the light is still on 可知灯亮着,即关灯的动作没有发生,因此用forget to do sth.
而forget doing sth表示灯已经关上了,而自己忘记了这一事实.此处不符合题意.

forget to do 忘了将要做的某事
forget doing忘记做过的某事

forget to do 是 忘记做某事.. (实际上没有做)
forget doing 是 做了某事但忘了做过了.. 比如说我放学关窗了，但我忘了我曾经关了窗子，就说I forget closing the window.