请教WM手机软件开发中怎么打开屏幕呢

请问WM手机软件开发中如何打开屏幕呢
我在做一个定时的软件（C#），现在到了时间它会自动执行一个程序，但是屏幕却还是关闭的状态下，请问怎么开启屏幕呢，谢谢大家！最好能给源码，我百度谷歌找了好久没找到。

[解决办法]

C# code

 public enum PowerState//电池状态        {            PwrDeviceUnspecified = -1,            FullOn = 0,                       LowOn = 1,                       Standby = 2,                     Sleep = 3,                     Off = 4,               PwrDeviceMaximum = 5        }        [DllImport("CoreDll", SetLastError = true)]        static extern IntPtr SetPowerRequirement(string DeviceName, PowerState State, uint dwDeviceFlags, string Name, ulong Reserved);        [DllImport("CoreDll", SetLastError = true)]        static extern int ReleasePowerRequirement(IntPtr hPowerReq);        [DllImport("coredll.dll")]        private static extern int DevicePowerNotify(string device, PowerState deviceState, int deviceFlags);DevicePowerNotify("BKL1:", PowerState.FullOn, 1);//开背景灯DevicePowerNotify("BKL1:", PowerState.Off, 1);//关背景灯