There has been quite some activity regarding libdiscid in the last few months, here is some more: I have released dotnet-discid 0.2 which provides .NET / Mono bindings for libdiscid. The source is available at GitHub. For easy usage Windows users might want to use the NuGet package. Alternatively you can download source and binary releases at http://users.musicbrainz.org/~outsidecontext/dotnet-discid/. To use the assembly you will also need the native libdiscid release (e.g. discid.dll on Windows or any other native package for your platform). On Unix-like platforms you can just use the system wide installation of libdiscid.
No API docs yet, but the examples on Github will get you started. The library should be straight forward to use. This is an early release but it supports all the features provided by the latest libdiscid 0.5 (while still supporting earlier versions). I don’t expect many changes in the API but I will provide better documentation soon.