如何仅在 Windows Phone 8 应用程序中通过听筒播放音频

我尝试过使用 AudioRoutingManager 类...但我遇到了未经授权的访问异常.这是我的代码

I have tried with AudioRoutingManager class...but i got unauthorizedaccess exception. here is my code

 AudioRoutingManager audioRouting = AudioRoutingManager.GetDefault();
    public AudioRoutingEndpoint ChangeAudioRoute()
    {

       var currentEndPoint= audioRouting.GetAudioEndpoint();
       switch (currentEndPoint)
       {
           case AudioRoutingEndpoint.Earpiece:
           case AudioRoutingEndpoint.Default:
               return AudioRoutingEndpoint.Speakerphone;

           case AudioRoutingEndpoint.Speakerphone:
               return AudioRoutingEndpoint.Earpiece;

               default:
               throw new OperationCanceledException();
       }
    }

    public void SetAudioRoute()
    {
        audioRouting.SetAudioEndpoint(this.ChangeAudioRoute());
    }