I've never been asked for code samples, seems somewhat pointless as they're easy to copy from somewhere else.
In my first job as a programmer I had to sit a programming test as part of the second interview. At least that
proves that it's your code.
Other than that, I've found employers have taken it for granted that I can code -- probably because I'm a senior programmer -- and have only been interested in the types of projects I have worked on.
Maybe it's different here in the UK, and employers are just slacking.
Herbie