using System;

public class Program

{

    public static void Main()

    {

        var dt1 = DateTime.Now;

        var dt2 = DateTime.Now.AddDays(1);

        Console.WriteLine(dt1.Month == dt2.Month);

        Console.WriteLine("======");

        new A();

        Console.WriteLine("======");

        var a = new A("Hi");

          if (a.Person?.UserId != 0){

                Console.WriteLine("id=f");

              Console.WriteLine(a.Person.UserId);

          }

    }

}

​

class Base

{

    public Base(string message) 

    {

        Console.WriteLine(message);

    }

    public Base()

    {

        Console.WriteLine("Base");

    }

}

​

class A : Base

{

    public A(string message) : base(message)

    {

    }

    public A()

    {

        Console.WriteLine("A");

    }

    public Person Person{get;set;}

}

​

    public class Person

    {

        public int UserId{get;set;}

    }