win32api.cs

  const uint EVENT_SYSTEM_END = 0x00FF;
        const uint EVENT_MIN = 0x00000001;
        private void button1_Click(object sender, EventArgs e)
        {

            if (windowEventHook == IntPtr.Zero)
            {
                var threadId = 0;
                var processId = Process.GetCurrentProcess().Id;
                windowEventHook = SetWinEventHook(
                    EVENT_MIN,
                    EVENT_SYSTEM_END,
                    IntPtr.Zero,
                   WindowEventCallback,
                   0, 0,
                 WINEVENT_OUTOFCONTEXT | WINEVENT_SKIPOWNPROCESS
                   );
            }
        }

        private void WindowEventCallback(IntPtr hWinEventHook, uint eventType, IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime)
        {
            LogText("Event" + eventType);
        }

        void LogText(string message)
        {
            richTextBox1.Text += message + Environment.NewLine;
        }
        private static IntPtr windowEventHook;


        private delegate void WinEventProc(IntPtr hWinEventHook, uint eventType, IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime);

        [DllImport("user32.dll", SetLastError = true)]
        private static extern IntPtr SetWinEventHook(uint eventMin, uint eventMax, IntPtr hmodWinEventProc, WinEventProc lpfnWinEventProc, int idProcess, int idThread, int dwflags);
        [DllImport("user32.dll", SetLastError = true)]
        private static extern int UnhookWinEvent(IntPtr hWinEventHook);

        private const int WINEVENT_INCONTEXT = 4;
        private const int WINEVENT_OUTOFCONTEXT = 0;
        private const int WINEVENT_SKIPOWNPROCESS = 2;
        private const int WINEVENT_SKIPOWNTHREAD = 1;

        private const int EVENT_SYSTEM_FOREGROUND = 3;