using System;

​

public class Program

{

    public static void Main(string[] args)

    {

        Print("123");

        Print(DateTime.Now);

        Print(new int[] {1, 3, 5, 7});

        Print(123.44);

    }

​

    static void Print(object obj)

    {

        switch (obj)

        {

            case null:

                return;

            case string s:

                Console.WriteLine($"{s.Length}");

                break;

            case DateTime date:

                Console.WriteLine(date.Year);

                break;

            case int[] numbers when (numbers.Length > 0): // 可以使用 when 來指定其他條件。

                foreach (int n in numbers)

                    Console.Write(n + " ");

                Console.WriteLine();

                break;

            default:

                Console.WriteLine(obj.ToString());

                break;

        }

    }

}