The boilerplate is pretty minimal nowadays. In 2020, C# introduced top-level statements, which removed a lot of the ceremony.

You used to have a class, and there would typically be a separate Startup.cs file. Today, this is a complete .cs file for creating an API:

    var builder = WebApplication.CreateBuilder(args);
    var app = builder.Build();

    app.MapGet("/", () => "Hello World!");

    app.Run();

Nope. Take a look at Minimal API in .net 6 and onwards.

"Hello world" is a one-liner Since .Net 6.