运用C#设计一个模拟播放器控制台应用程序。定义接口IPlayer包含5个返回值为字符串的方法：播放Play 、停止Stop 、暂停Pause 、上一首Pre 、下一首Next 。定义接口IPlayer的派生类MP3。主函数功能：1声明一个MP3对象。2获取用户的一行输入。a当输入0时程序结束。b当输入1时模拟播放功能输出Playing music。c当输入为2时模拟停止功能输出Stop play。

using System;

interface IPlayer { string Play(); string Stop(); string Pause(); string Pre(); string Next(); }

class MP3 : IPlayer { public string Play() { return "Playing music."; }

public string Stop()
{
    return "Stop play.";
}

public string Pause()
{
    return "Suspend play.";
}

public string Pre()
{
    return "Previous song.";
}

public string Next()
{
    return "Next song.";
}

}

class Program { static void Main(string[] args) { MP3 mp3 = new MP3(); while (true) { int input = Convert.ToInt32(Console.ReadLine()); switch (input) { case 0: return; case 1: Console.WriteLine(mp3.Play()); break; case 2: Console.WriteLine(mp3.Stop()); break; case 3: Console.WriteLine(mp3.Pause()); break; case 4: Console.WriteLine(mp3.Pre()); break; case 5: Console.WriteLine(mp3.Next()); break; default: Console.WriteLine("Inputting illegal characters."); break; } } }