pInvoke used in real WP7 app

public static class Core
{
    public static void Mute()
    {
        uint num = 0;
        Core.waveOutGetVolume(IntPtr.Zero, out num);
        Core.waveOutSetVolume(IntPtr.Zero, 0);
        IsolatedStorageSettings.ApplicationSettings.AddOrUpdateValue("volume", num);
    }

    public static void UnMute()
    {
        if (IsolatedStorageSettings.ApplicationSettings.Contains("volume"))
        {
            uint item = (uint)IsolatedStorageSettings.ApplicationSettings["volume"];
            Core.waveOutSetVolume(IntPtr.Zero, item);
        }
    }

    [DllImport("coredll.dll", CharSet=CharSet.None)]
    private static extern int waveOutGetVolume(IntPtr device, out uint volume);

    [DllImport("coredll.dll", CharSet=CharSet.None)]
    private static extern int waveOutSetVolume(IntPtr device, uint volume);
}