For those who don't know ATL yet, it allows you to read info (tags, duration, bitrate...) from various audio files formats. As for the Delphi version, the source of its port is entirely available and ready to use for any C# programmer.
=> Get it here (scroll down the page for the announcement)
NB : Since I've done the job for the needs of my own project (Ethos Cataloger), I've only tested the reading features. All the tag editing features can be compiled but haven't been tested at all !
If you have some time on your hands, you can debug it yourself and hopefully add your contribution to make a better ATL