Wiki markup to HTML converter?

[Yourself]

Are there any freely licensed Wiki markup to HTML converters available?

Basically, I don't want to convert full wiki markup, just very basic inline
formatting (specically options for bold, italic, and underline text, and
creating hyperlinks)

So the user would type in e.g. [http://www.example.org], i'd pass that to a
wiki converter function, and that would return HTML markup.

I've found client side solutions written in JavaScript, but I'm after a
server side solution to run in .NET