c# – enum and const

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    /// <summary>
    /// 定义枚举类型性别,只有两个值Male和Female
    /// </summary>
    enum Gender
    {
        Male,
        Female
    }
    class Program
    {
        //定义常量PI
        const double PI = 3.14;
        static void Main(string[] args)
        {
            Gender sex;
            sex = Gender.Male;
            switch (sex)
            {
                case Gender.Male:
                    Console.Write("是个男的");                    
                    break;
                case Gender.Female:
                    Console.Write("是个女的");
                    break;
            }
            Console.ReadKey();
        }
    }
}