```XMAL

<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"   

xmlns:d="http://schemas.microsoft.com/expression/blend/2008"   

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"   

xmlns:hc="https://handyorg.github.io/handycontrol"   

xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"   

xmlns:qk="https://getquicker.net"  

    Title="MP3 Player" Height="150" Width="300">  

    <Grid>  

        <!-- 定义三行三列 -->  

        <Grid.ColumnDefinitions>  

            <ColumnDefinition Width="Auto"/>  

            <ColumnDefinition Width="*"/>  

            <ColumnDefinition Width="Auto"/>  

        </Grid.ColumnDefinitions>  

        <Grid.RowDefinitions>  

            <RowDefinition Height="Auto"/>  

            <RowDefinition Height="*"/>  

            <RowDefinition Height="Auto"/>  

        </Grid.RowDefinitions>  

        <!-- 在第一行第一列放置一个按钮 -->  

        <Button Name="playButton" Content="playButton" Grid.Column = "0" Grid.Row = "0"/>  

        <Button Name="pauseButton" Content="pauseButton" Grid.Column = "0" Grid.Row = "1"/>  

        <!-- 在第二行第二列放置一个列表 -->  

        <ListBox Name = "mp3List" Grid.Column = "1" Grid.Row = "1"/>  

        <!-- 在第三行跨越三列放置一个进度条 -->  

        <ProgressBar Name = "mp3Progress" Grid.Column = "0" Grid.Row = "2"  

                     Grid.ColumnSpan = "3"/>  

    </Grid>  

</Window>

```

```cs

using Quicker.Public;   

using System.Windows;   

using System.Windows.Controls;   

using System.Collections.Generic;   

using NAudio.Wave;  

using Microsoft.Win32;   

using System.Net;  

// ...  

// 声明一个类级别的字段  

public static IWavePlayer waveOutDevice;  

public static void OnWindowCreated(Window win, IDictionary<string, object> dataContext,ICustomWindowContext winContext){  

Button playButton = win.FindName("playButton") as Button;  

playButton.Click += playButton_Click;  

Button pauseButton = win.FindName("pauseButton") as Button;  

pauseButton.Click += pauseButton_Click;  

}  

public static void playButton_Click(object sender, EventArgs e){  

// 判断 waveOutDevice 是否存在  

if(waveOutDevice != null){  

    // 判断 waveOutDevice 的播放状态是否是暂停  

    if(waveOutDevice.PlaybackState == PlaybackState.Paused){  

        // 调用 Play 或 Resume 方法恢复播放  

        waveOutDevice.Play();  

        //waveOutDevice.Resume();  

        // 结束方法  

        return;  

    }  

    // 判断 waveOutDevice 的播放状态是否是播放  

    if(waveOutDevice.PlaybackState == PlaybackState.Playing){  

        // 不执行任何操作  

        return;  

    }  

}  

// 如果 waveOutDevice 不存在或者不是暂停或者播放状态，就像之前一样初始化并播放音乐  

// 创建一个 WaveOutEvent 的实例并赋值给字段  

waveOutDevice = new WaveOutEvent ();  

string path = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);  

string filePath = System.IO.Path.Combine(path, "邂逅你的春天.mp3");  

using (var client = new System.Net.WebClient())  

{  

    client.DownloadFile("http://music.163.com/song/media/outer/url?id=2031874714.mp3", filePath);  

}  

AudioFileReader audioFileReader = new AudioFileReader (filePath);  

waveOutDevice.Init (audioFileReader);  

waveOutDevice.Play ();  

}  

public static void pauseButton_Click(object sender, EventArgs e){  

    try{  

        // 访问字段  

        if(waveOutDevice != null){  

            waveOutDevice.Pause ();  

        }  

    }  

    catch(Exception ex){  

        MessageBox.Show(ex.Message);  

    }  

}

```