using System;

using static System.Console;

​

public class Program {

    public static void Main() {

        var numero = 123;

        Func<string, string> func = numero.ToString;

        WriteLine(func("000000"));

        Func<string> func2 = numero.ToString;

        WriteLine(func2());

        Action<string> a = delegate(string txt) { WriteLine(txt); };

        Action<string> b = txt => WriteLine(txt);

        Action<string> c = WriteLine;

        a("abc");

        b("abc");

        c("abc");

    }

}