[SOLVED] Single player: Enabling Cheats?

Note: I'm not talking about anything on a multilayer server, I despise cheating when it involves other players.

Ok, so I occasionally like to play around with cheat codes in Single player games ... but no matter what I do it just won't let me do it at all! And yes, I've even tried using

Code:

sendcvar sv_cheats "0"

and such other similar commands, but that just isn't working at all!

What do I need to change or what command must I type to enable cheats in a single player game?

sv_cheats 1

1 turns stuff on, 0 turns it off.

But you either have to restart the map or set it before start the map. Does not need "sendcvar".