在具有媒体元素的独立存储中播放wav文件

我创建了一个小应用程序来录制和播放语音，用这个代码制作了一个录制按钮和一个播放按钮。

我测试了应用程序，录音机工作正常（我使用"Windows手机电源工具"从WP模拟器的隔离存储中获取tempAudio.wav，这个音频文件可以播放），但播放按钮没有播放声音，我找不到btPlay按钮有任何问题：（

XAML代码（两个按钮是往返按钮和来自coding4fun工具箱的往返按钮）

<StackPanel Orientation="Horizontal">
    <toolkit1:RoundToggleButton x:Name="btRecorder" IconUri="..." Checked="btRecorder_Checked" checked="btRecorder_Unchecked"/> 
    <MediaElement x:Name="meVoicePlayer" AutoPlay="False"/>
    <toolkit1:RoundButton x:Name="btPlay" Click="PlayAudio_Click" IconUri="..."/>
</StackPanel>

c#代码

MicrophoneRecorder recorder = new MicrophoneRecorder();
private void btRecorder_Checked(object sender, RoutedEventArgs e)
    {
        recorder.Start();                       
    }
private void btRecorder_Unchecked(object sender, RoutedEventArgs e)
    {
        recorder.Stop();
        SaveTempAudio(recorder.Buffer);
    }
public void SaveTempAudio(MemoryStream buffer)
    {
        using (IsolatedStorageFile isf = IsolatedStorageFile.GetUserStoreForApplication())
        {
            var bytes = buffer.GetWavAsByteArray(recorder.SampleRate);                
            using (IsolatedStorageFileStream audio = new IsolatedStorageFileStream("TempAudio.wav",FileMode.Create,isf))
            {
                audio.Write(bytes, 0, bytes.Length);
            }
        }
    }
private void PlayAudio_Click(object sender, RoutedEventArgs e)
    {
    using (IsolatedStorageFile isf = IsolatedStorageFile.GetUserStoreForApplication())
        {                
            using (IsolatedStorageFileStream audio = new IsolatedStorageFileStream("TempAudio.wav",FileMode.Open,isf))
            {
                meVoicePlayer.Stop();
                meVoicePlayer.SetSource(audio);
                meVoicePlayer.Position = new TimeSpan(0, 0, 0, 0);
                meVoicePlayer.Play();
            }
        } 
    }