c# How to get the events when the screen/display goes to power OFF or ON?

Question

Hi I have been searching but I can\'t find the answer. How do I know when the screen is going off or on. Not the SystemEvents.PowerModeChanged . I dont know how to retrieve

Answer 1

This works for me even MainWindow is hidden. The code is based on above post, and C++ code of https://www.codeproject.com/Articles/1193099/Determining-the-Monitors-On-Off-sleep-Status.

public partial class MainWindow : Window
    {
        private readonly MainViewModel VM;
        private HwndSource _HwndSource;
        private readonly IntPtr _ScreenStateNotify;

        public MainWindow()
        {
            InitializeComponent();
            VM = DataContext as MainViewModel;

            // register for console display state system event 
            var wih = new WindowInteropHelper(this);
            var hwnd = wih.EnsureHandle();
            _ScreenStateNotify = NativeMethods.RegisterPowerSettingNotification(hwnd, ref NativeMethods.GUID_CONSOLE_DISPLAY_STATE, NativeMethods.DEVICE_NOTIFY_WINDOW_HANDLE);
            _HwndSource = HwndSource.FromHwnd(hwnd);
            _HwndSource.AddHook(HwndHook);
        }

        private IntPtr HwndHook(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
        {
            // handler of console display state system event 
            if (msg == NativeMethods.WM_POWERBROADCAST)
            {
                if (wParam.ToInt32() == NativeMethods.PBT_POWERSETTINGCHANGE)
                {
                    var s = (NativeMethods.POWERBROADCAST_SETTING) Marshal.PtrToStructure(lParam, typeof(NativeMethods.POWERBROADCAST_SETTING));
                    if (s.PowerSetting == NativeMethods.GUID_CONSOLE_DISPLAY_STATE)
                    {
                        VM?.ConsoleDisplayStateChanged(s.Data);
                    }
                }
            }

            return IntPtr.Zero;
        }

        ~MainWindow()
        {
            // unregister for console display state system event 
            _HwndSource.RemoveHook(HwndHook);
            NativeMethods.UnregisterPowerSettingNotification(_ScreenStateNotify);
        }
    }

And Native methods here:

internal static class NativeMethods
{
    public static Guid GUID_CONSOLE_DISPLAY_STATE = new Guid(0x6fe69556, 0x704a, 0x47a0, 0x8f, 0x24, 0xc2, 0x8d, 0x93, 0x6f, 0xda, 0x47);
    public const int DEVICE_NOTIFY_WINDOW_HANDLE = 0x00000000;
    public const int WM_POWERBROADCAST = 0x0218;
    public const int PBT_POWERSETTINGCHANGE = 0x8013;

    [StructLayout(LayoutKind.Sequential, Pack = 4)]
    public struct POWERBROADCAST_SETTING
    {
        public Guid PowerSetting;
        public uint DataLength;
        public byte Data;
    }

    [DllImport(@"User32", SetLastError = true, EntryPoint = "RegisterPowerSettingNotification", CallingConvention = CallingConvention.StdCall)]
    public static extern IntPtr RegisterPowerSettingNotification(IntPtr hRecipient, ref Guid PowerSettingGuid, Int32 Flags);



    [DllImport(@"User32", SetLastError = true, EntryPoint = "UnregisterPowerSettingNotification", CallingConvention = CallingConvention.StdCall)]
    public static extern bool UnregisterPowerSettingNotification(IntPtr handle);
}