using System;

using System.Linq;

​

class Program {

    static string? calc1() => null;

    static string? calc2() => "hi";

    static string? calc3() => null;

    static string? calc4() => "everyone";

    static void Main() {

        var list = new [] { calc1(), calc2(), calc3(), calc4() }.Where(x => x != null).ToList();

        list.ForEach(Console.WriteLine);

    }

}