I use Mono Develop on Raspian Stretch and added GTK so I could create GUIs. You can add wiringpi for accessing GPIO ports. It worked fairly well on a Pi 3B+. Unfortunately it has been removed from the repository so I can't use it with Pi 4 and Buster.
I'm looking for a replacement now. Visual Studio Code sounds interesting if I can find something to create decent GUIs with it.