Auf GlobaleEvents mit dem .NET Framework reagieren

Globale Events können mit dem .NET Framework über die Win32-Funktion SetWindowsHookEx behandelt werden. Allerdings lassen sich nur die beiden low-level Hooks WH_KEYBOARD_LL und WH_MOUSE_LL behandeln.

Win32-Funktionen:

    public class Win32Helper
    {


      [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
      public static extern IntPtr SetWindowsHookEx(int idHook,
          LowLevelMouseProc lpfn, IntPtr hMod, uint dwThreadId);


      public delegate IntPtr LowLevelMouseProc(int nCode, IntPtr wParam, IntPtr lParam);


      [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
      [return: MarshalAs(UnmanagedType.Bool)]
      public static extern bool UnhookWindowsHookEx(IntPtr hhk);


      [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
      public static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode,
          IntPtr wParam, IntPtr lParam);



      [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
      public static extern IntPtr GetModuleHandle(string lpModuleName);

   
   
      [StructLayout(LayoutKind.Sequential)]
      public class POINT
      {
          public int x;
          public int y;
      }

   
      [StructLayout(LayoutKind.Sequential)]
      public struct MSLLHOOKSTRUCT
      {
          public POINT pt;
          public uint mouseData;
          public uint flags;
          public uint time;
          public IntPtr dwExtraInfo;
      }

      public enum MouseMessages
      {
          WM_LBUTTONDOWN = 0x0201,
          WM_LBUTTONUP = 0x0202,
          WM_MOUSEMOVE = 0x0200,
          WM_MOUSEWHEEL = 0x020A,
          WM_RBUTTONDOWN = 0x0204,
          WM_RBUTTONUP = 0x0205,
      }      

  
      public enum WindowsHookCodes : int
      {

          WH_KEYBOARD = 2,
          WH_MOUSE = 7,
          WH_KEYBOARD_LL = 13,
          WH_MOUSE_LL = 14
      }
    }

Die Klasse HookHelper kapselt den Zugriff auf die Win32-Funktionen und stellt ein Event bereit, auf das sich andere Klassen registrieren können.

  public class HookHelper
  {
      private static Win32Helper.LowLevelMouseProc _proc = LowLevelMouseHookProc;
      private static readonly ILog log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

      public delegate void GlobalMouseListener(int code, IntPtr wParam, Win32Helper.MSLLHOOKSTRUCT hookStruct);

      public static event GlobalMouseListener GlobalMouseListenerEvent;

      private static IntPtr hGlobalMouseHook;

      public static bool StartGlobalMouseHook()
      {
          using (Process currentProcess = Process.GetCurrentProcess())
          {
              using (ProcessModule currentModule = currentProcess.MainModule)
              {
                  hGlobalMouseHook = Win32Helper.SetWindowsHookEx((int)Win32Helper.WindowsHookCodes.WH_MOUSE_LL,
                              _proc,
                              Win32Helper.GetModuleHandle(currentModule.ModuleName),
                               0);
                  if (hGlobalMouseHook.ToInt32() == 0)
                  {
                      log.Error("SetWindowsHookEx Failed");
                      return false;
                  }
                  log.Debug("SetWindowsHookEx called for " + hGlobalMouseHook + " with sucess");
                  return true;
              }
          }

      }

      /// <summary>
      /// Stoppt den globalen Maus-Hook.
      /// </summary>
      public static void StopGlobalMouseHook()
      {

          bool b = Win32Helper.UnhookWindowsHookEx(hGlobalMouseHook);
          if (b)
          {
              log.Debug("StopGlobalMouseHook called for " + hGlobalMouseHook + " with sucess");
          }
          else
          {
              log.Error("StopGlobalMouseHook called for " + hGlobalMouseHook + " failed");
          }
      }

      /// <summary>
      /// Diese Methode wird im Falle gerufen im Falle des MouseHooks.
      /// Sorgt dafuer, dasd die EventListener von GlobalMouseListenerEvent gerufen werden.
      /// </summary>
      /// <param name="nCode"></param>
      /// <param name="wParam"></param>
      /// <param name="lParam"></param>
      /// <returns></returns>   
      private static IntPtr LowLevelMouseHookProc(int nCode, IntPtr wParam, IntPtr lParam)
      {

          Win32Helper.MSLLHOOKSTRUCT hookStruct = (Win32Helper.MSLLHOOKSTRUCT)Marshal.PtrToStructure(lParam, typeof(Win32Helper.MSLLHOOKSTRUCT));

          if (GlobalMouseListenerEvent.GetInvocationList().Length > 0)
          {
              GlobalMouseListenerEvent(nCode, wParam, hookStruct);
          }

          return Win32Helper.CallNextHookEx(hGlobalMouseHook, nCode, wParam, lParam);
      }

  }

In einem Form kann der HookHelper wie folgt verwendet werden:

  public MainForm()
  {
      InitializeComponent();

      HookHelper.GlobalMouseListenerEvent += new HookHelper.GlobalMouseListener(MyGlobalMouseListener);
      HookHelper.StartGlobalMouseHook();            
       ...
  }


  public void MyGlobalMouseListener(int code, IntPtr wParam, Win32Helper.MSLLHOOKSTRUCT hookStruct)
  {
      if (code >= 0 && Win32Helper.MouseMessages.WM_LBUTTONDOWN == (Win32Helper.MouseMessages)wParam)
      {
          System.Diagnostics.Trace.WriteLine(hookStruct.pt.x + ", " + hookStruct.pt.y);
      }
  }