Well, chiropodists like jokes. But opticians like them.
Because he didn't see the funny side to it.
Three. One to post it, another to post a better punchline in the comment section, and another to repost it with the new punchline.
Prism (Note: I made this joke up. Sorry if this little note refracts from the humour.)
Germany.
Driver
Because he didn't C#