window mobile 防止系统休眠代码

window mobile 过一段时间就会自动休眠，下面的代码可以禁止机器自动休眠。

[DllImport("CoreDll.dll")]
        private static extern void SystemIdleTimerReset();

        private static int nDisableSleepCalls = 0;
        private static System.Threading.Timer preventSleepTimer = null;

        private static void PokeDeviceToKeepAwake(object extra)
        {
            try
            {
                SystemIdleTimerReset();
            }
            catch (Exception e)
            {
                // TODO
            }
        }


        /// <summary>
        /// 禁止设备自动关闭电源
        /// </summary>
        public static void DisableDeviceSleep()
        {
            nDisableSleepCalls++;
            if (nDisableSleepCalls == 1)
            {
                // 没隔30秒刷新一次计时器
                preventSleepTimer = new System.Threading.Timer(new System.Threading.TimerCallback

              (PokeDeviceToKeepAwake),
                null, 0, 10 * 1000);
            }
        }

        /// <summary>
        /// 允许设备自动关闭电源
        /// </summary>
        public static void EnableDeviceSleep(){
            nDisableSleepCalls--;
            if (nDisableSleepCalls == 0){
                if (preventSleepTimer != null){
                    preventSleepTimer.Dispose();
                    preventSleepTimer = null;
                }
            }
        }