.NET Core

.NET Core is fully linux compatible and can be developed using Visual Studio Code. All free! Finally, Micro$soft...

This was a pretty easy method:

Install vs code
Grab an existing project
Open it in vs code
Let vs code install all the support extensions, including C#. You might have to restart code a couple times to get it eventually be happy. Not bad!

Everything is eventually done on the command line, here's the reference.