Switch ScreenPower

 public class Screen
        {
            private const uint QUERYESCSUPPORT = 8;
            private const uint GETVFRAMEPHYSICAL = 6144;
            private const uint GETVFRAMELEN = 6145;
            private const uint DBGDRIVERSTAT = 6146;
            private const uint SETPOWERMANAGEMENT = 6147;
            private const uint GETPOWERMANAGEMENT = 6148;
            private const int SHFS_SHOWSTARTICON = 0x0010;
            private const int SHFS_HIDESTARTICON = 0x0020;
            public static void PowerOff()
            {
                IntPtr hdc = GetDC(IntPtr.Zero);
                uint size = 12;
                byte[] vpm = new byte[size];
                BitConverter.GetBytes(size).CopyTo(vpm, 0);
                BitConverter.GetBytes(0x0001).CopyTo(vpm, 4);
                BitConverter.GetBytes((uint)ScreenPowerState.ScreenPowerOff).CopyTo(vpm, 8);
                ExtEscapeSet(hdc, SETPOWERMANAGEMENT, size, vpm, 0, IntPtr.Zero);
            }

             public static void PowerOn()
            {
                IntPtr hdc = GetDC(IntPtr.Zero);

                uint size = 12;
                byte[] vpm = new byte[size];

                BitConverter.GetBytes(size).CopyTo(vpm, 0);
                BitConverter.GetBytes(0x0001).CopyTo(vpm, 4);
                BitConverter.GetBytes((uint)ScreenPowerState.ScreenPowerOn).CopyTo(vpm, 8);

                ExtEscapeSet(hdc, SETPOWERMANAGEMENT, size, vpm, 0, IntPtr.Zero);
            }

            [DllImport("coredll", EntryPoint = "ExtEscape")]
            private static extern int ExtEscapeSet(
                IntPtr hdc,
                uint nEscape,
                uint cbInput,
                byte[] lpszInData,
                int cbOutput,
                IntPtr lpszOutData
                );

            [DllImport("coredll")]
            private static extern IntPtr GetDC(IntPtr hwnd);
        }

         public enum ScreenPowerState : uint
        {
             ScreenPowerOn = 1,
            ScreenPowerStandBy,
             ScreenPowerSuspend,
             ScreenPowerOff
        }