In the uncompressed situation I know I need to read the wav header, pull out the number of channels, bits, and sample rate and work it out from there:
(channels) * (bits) *
I'm gonna have to say MediaInfo, I have been using it for over a year with a audio/video encoding application I'm working on. It gives all the information for wav files along with almost every other format.
MediaInfoDll Comes with sample C# code on how to get it working.