By default, Pixel Vision 8 will automatically create a Lua game project. The Workspace Explorer uses the same template for all new game projects, which includes a code.lua file.
You can switch to C# at any time by opening the info.json file and changing the game engine to C#.
Once you switch over to the C# runner, you will need to create a new code file since the game will no longer run with the default code.lua script.
The Workspace Explorer automatically detects the runner to use and creates either a Lua or C# script file for you whenever you select New Code from the drop-down menu. You can also tell which runner you are using by the code icons. If the game's runner can not use the code file, it will change color.
You can edit C# files just like you would Lua, and you can have multiple C# files in a single project. The biggest issue to pay attention to will be giving each code file a unique class name and importing the correct code libraries.
If you run the C# game using Ctrl + R, it will load the default code.cs file along with any other C# files in the project. Since the C# code is re-compiled at run-time, there may be a pause while loading. If there are no errors, you will be able to play your C# game.