C# 面向对象例题 -- Mp3功能实现

        using System;
        using System.Collections.Generic;
        using System.Linq;
        using System.Text;
        using System.Threading.Tasks;
        namespace 面向对象7._13_Mp3完善
        {
        class Program
         {
        static void Main(string[] args)
         {
         PlaySong ps = new PlaySong();
         ps.Inof();
         Console.ReadLine();
         }
         }
        //歌曲信息列表
        class Song
         {
        public Song() { }
        public Song(String title, string singer, int length)
         {
        this.titile = title;
        this.singer = singer;
        this.length = length;
         }
        ///
        /// 歌曲名
        ///
        public String titile{set;get;}
        public String singer { set; get; }
        public int length { set; get; }
         }
        class PlaySong
         {
         List list = new List();
        ///
        /// 载入本地歌曲
        ///
        private int listLenght;  //获取到列表长度（有几首歌）
        public void bianli() {
         listLenght = 0;
        foreach (Song item in list)
         {
         Console.Write(" " +(listLenght+1)+"."+item.titile+" - "+item.singer+" ");
         time(item.length);
         listLenght++;
         }
         }
        public void Inof()
         {
         Console.WriteLine("您的当前播放列表是：");
         Console.WriteLine();
         Console.WriteLine("++ ——————————— ++");
         Console.WriteLine();
         bianli();
         Console.WriteLine();
         Console.WriteLine("++ ——————————— ++");
         Console.WriteLine();
         Console.WriteLine(" 请您输入功能序号 ：");
         Console.WriteLine();
         Console.WriteLine("1.播放歌曲 2.载入本地歌曲 3.上一首 4.下一首 5.暂停 6.添加歌曲 7.退出播放器");
        int n = int.Parse(Console.ReadLine());
        switch (n)
         {
        case 1:
         play();
        break;
        case 2:
         load();
        break;
        case 3:
         upSong();
        break;
        case 4:
         downSong();
        break;
        case 5:
         stop();
        break;
        case 6:
         downLoad();
        break;
        case 7:
        return;
        default :
        break;
         }
         }
        public void load()
         {
         Song s1 = new Song("灰色头像", "许嵩", 356);
         Song s2 = new Song("坏孩子", "许嵩", 303);
         Song s3 = new Song("城府", "许嵩", 287);
         Song s4 = new Song("因为了解", "汪苏泷", 196);
         Song s5 = new Song("送你的读白", "许嵩", 314);
         list.Add(s1);
         list.Add(s2);
         list.Add(s3);
         list.Add(s4);
         list.Add(s5);
         Console.WriteLine("++ ——————————— ++");
         Console.WriteLine();
         bianli();
         Console.WriteLine();
         Console.WriteLine("++ ——————————— ++");
         Inof();
         }
        public void downLoad()
         {
         Song s = new Song();
         Console.Write("请输入您要下载的歌曲名称：");
         s.titile = Console.ReadLine();
         Console.Write("请输入您要下载的歌手名称：");
         s.singer = Console.ReadLine();
         Console.Write("请输入您要下载歌曲的时长：");
         s.length =int.Parse( Console.ReadLine());
         list.Add(s);
         listLenght++;
         Console.WriteLine("您的歌曲下载成功！");
         Console.WriteLine();
         Inof();
         }
        private int index = 0; //记录播放的歌曲
        public void play()
         {
         Console.WriteLine();
        if (index < 0)
         {
         Console.WriteLine("当前列表没有歌曲！");
         }
        if (index < listLenght)
         {
         Console.WriteLine("正在播放：" + list[index].titile);
         }
         Console.WriteLine();
         Inof();
         }
        public void upSong()
         {
        if (index < 0) {
         Console.WriteLine("当前列表没有歌曲");
         }
         index = index - 1 < 0 ?  0: index - 1;
        if (index - 1 < 0)
         {
         Console.WriteLine("当前播放已经是第一首音乐：" + list[0].titile);
         }
        else
         {
         Console.WriteLine("正在播放：" + list[index].titile);
         }
         Console.WriteLine();
         Inof();
         }
        public void downSong()
         {
        if (index < 0)
         {
         Console.WriteLine("当前列表没有歌曲");
         }
         index = index + 1 > listLenght ? listLenght : index+1;
        if (index +1 > listLenght)
         {
         Console.WriteLine("当前播放已经是最后一首音乐：");
         }
        else
         {
         Console.WriteLine("正在播放：" + list[index].titile);
         }
         Console.WriteLine();
         Inof();
         }
        public void stop()
         {
         Console.WriteLine("暂停播放："+list[index].titile);
         Console.WriteLine();
         Inof();
         }
        ///
        /// 转换时间格式 00:00:00 
        ///
        ///
        public void time(int time)
         {
         TimeSpan ts = new TimeSpan(0, 0, time);
         Console.WriteLine(" " + (ts.Minutes).ToString().PadLeft(2, '0') + ":" + (ts.Seconds).ToString().PadLeft(2, '0'));
         }
         }
        }