--Why did Germany not invade Switzerland in World War 2?

--Just because Switzerland declared itself as neutral, Germany did not invade it?

--If Austria/Poland had declared themselves as neutral, would that mean Germany would not have invaded these countries?

--This is a cross post. I posted this earlier today in /r/history, and folks there suggested to post it here as well for an informed answer.

--http://www.reddit.com/r/history/comments/29rii1/how_did_switzerland_remain_neutral_during_world/

--I was always taught in history back in school that Switzerland remained neutral. No explanation as such was provided then.