audio file

You might be able to do this using Windows Media Player. You can find more information here:
http://www.levibotelho.com/development/get-the-length-of-a-video-in-c/

But this class doesn't provide full information about the media file, such as number of audio Channels, average bit rate, etc. In this case, you might need to use a programming toolkit like leadtools that is specialized in Multimedia.