I tried to use Gui.cs and wasn't able to. It has a lot of rough edges and I had to move on because it wasn't well fleshed out.

Other/better .NET libraries include:

https://github.com/spectresystems/spectre.console

https://github.com/TomaszRewak/C-sharp-console-gui-framework

https://github.com/elw00d/consoleframework