Modernise please

[DickBaker]

code has unsightly unnecessary usings, doesn't use current idioms like file-scoped namespaces etc, and CSC flags 13 warnings

I will raise a PR with my suggestions to improve this excellent pattern tuition course.

BTW, pity that the PS Exercise files bunches all the demo code into chapter2, so all subsequent chapters in ZIP just contain the PDF material

[KevinDockx]

Hi Dick, glad to read you like the course! I'm actually working on a new version as we speak, which will target .NET8, C#12 & use new features/idioms where I can, so: modernization is coming up :) I can't accept PRs on this repo as I need it to stay in sync with the code samples I show in the course, but if you have a fork I'd be happy to have a look at your suggestions and see what I can incorporate in the new version.

[DickBaker]

have PR'ed anyway to simplify your diffs. Have a good day, Dick