I’ve been doing full time JS with some Ruby for the past 5 years. I doubt I could write anything more than “Hello world” in C# without a lot of Googling.
"I understand the concept of types and can read annotations but I’ve never written it. The few times I tried, I ran into difficulties."
I looked his github, and his only C# experience seems to be a tictactoe made in 2014.
I’ve worked on C# codebases professionally for about four years. They’re not open source because half of that time I worked on enterprise software (ASP .NET MVC, Entity Framework, NHibernate) and another half was a closed source product (Xamarin aka MonoTouch, Rx). Prior to that I worked a little on an open source static analysis tool (Gendarme) using Mono Cecil.
Prior to that I was moderating the .NET section on one of the largest Russian programming forums and translated documents like LINQ Overview when they came out. I also have a silver C# badge on StackOverflow. (https://stackoverflow.com/help/badges/39/c-sharp?userid=4581...)
I know how types work. My remark was that I haven’t worked with C# for about four years. I’m not aware of changes between versions 5 and 9, and might have forgotten some of the C# syntax for things like lambdas, having worked a lot with JS since then.
I’ve mentored a few junior devs in my day, and this kind of thing would have been really helpful to encourage them to keep pushing.