I want to find pitches in raw of wav file using FFT and etc. but before I should to decompress MP3 file. I am using C# with WinRT, and I'm very limited for third-party libraries which often cause exceptions.
You might try NLayer. It's purely managed code (with no P/Invoke), so it should run just fine in a WinRT app.
Disclaimer: I am a major contributor to NLayer.