You no longer need imports, or namespace, class and main method boilerplate to write a basic C# program; there’s now a way to simply write some lines of code in a file with some implicit imports, and compile/run them like it was more of a scripting language.
https://learn.microsoft.com/en-us/dotnet/csharp/tutorials/to...
(If there’s other syntax changes, I don’t know them, AFAIK it’s the same C# you write)