@fristi Personally I would highly disrecommend it, almost nothing Linux and libre uses C#, even video games where it's frequently used. Gnome and related pretty much dropped the apps that used it 5~10 years ago, and they're part of the reason for Mono getting more serious adoption over dotGNU.
@fristi Mostly C, C++ and Python. Sometimes Vala (gnome's own language), bits of Rust in very recent ones, sometimes Java.
After all those either have toolkits directly for the language or have more or less official bindings and so decent documentation. Using FFIs being quite a nightmare otherwise.