As promised I just released the first version of PortAudioSharp (v.0.19.1.41872).
PortAudioSharp is a managed library developed for both Mono/Linux and .NET/Windows; it provides .NET bindings for the portable low-latency audio API PortAudio v.19.
It's open-source and it has an LGPL license, so you can use it also in commercial projects if you simply use it as a library.
Please help me improve it!