What version?

What is the latest version of the C# language that you can use? I think 2.0 but I am not certain.

I believe we are on .NET 4.0 / MONO 3.5

in player settings i can choose between .net 2.0 subset + .net 2.0

.net 3.5 iirc.

So we can use the latest version of the language, but the library needs to be 2.0?

That’s what I get for not thinking in relation to Unity ha!

No you can not sue the latest version of the language. Its .NET 3.5 or below, you can’t make use of anything related to .NET 4+ and assemblies built for .NET 4+ will not work in unity either