How do you paste with vim without code being commented?

Before you paste, type this in normal mode:

:set paste

Then enter insert mode. You will see the status bar say insert (paste). Paste your code. Hit ESC to return to normal mode, and:

:set nopaste

You are no longer in paste mode.

Or, to avoid having to turn paste on and off, just put the text. Rather than going into insert mode and pasting, in command mode type:

"+p

The + buffer corresponds to the system clipboard.

If you insist on using paste, I'd suggest mapping something to toggle it. For example, :set pastetoggle=<F2> (wow, didn't realize there was a special option for that)