How to add CTRL+/ as shortcut key in VIM

Question

I want to use ctrl+/ as the shortcut key for commenting the current line
Adding nmap <C-/> ,cc is invalid, but backslash\ is OK
I hope everyone can help me see

Answer 1

vim中不能使用 ctrl+/ 作为快捷键.

You can't map Ctrl-/ in Vim because the only "Ctrl+printable key" characters which can be reliably mapped in Vim are those defined by the (already rather old) ASCII standard, which means the only printable keys which have a Ctrl counterpart are 0x3F to 0x5F plus the lowercase letters, as follows:

Ctrl+? (0x3F) = DEL (0x7F)
Ctrl+(key 0x40-0x5F) = subtract 0x40 from the printable character
Ctrl+lowercase = Ctrl+ the corresponding uppercase.

Nothing else. No Ctrl+digit and no Ctrl+slash (where / = 0x2F).

BTW, the above also explains why Vim cannot discriminate between

Ctrl-I and Tab (both 0x09, HT)
Ctrl-M and Enter (both 0x0D, CR)
Ctrl-[ and Esc (both 0x1B, ESC)

懒得翻译了，来自这里.