WindowsHook.cs

// ***********************************************************************
//  LocalWindowsHook class
//  Dino Esposito, summer 2002
//  With some cleanup by Dieter Menne (dieter menne at menne-biomed.de) in April 2011
//  Provide a general infrastructure for using Win32 
//  hooks in .NET applications
// 
// ***********************************************************************


using System;
using System.Runtime.InteropServices;
using System.Threading;

namespace RDotNet
{

  #region Class HookEventArgs

  // ReSharper disable InconsistentNaming
  public class HookEventArgs : EventArgs
  {
    public int HookCode; // Hook code
    public IntPtr wParam; // WPARAM argument
    public IntPtr lParam; // LPARAM argument
  }

  #endregion

  #region Enum HookType

  // Hook Types
  public enum HookType
  {
    WH_JOURNALRECORD = 0,
    WH_JOURNALPLAYBACK = 1,
    WH_KEYBOARD = 2,
    WH_GETMESSAGE = 3,
    WH_CALLWNDPROC = 4,
    WH_CBT = 5,
    WH_SYSMSGFILTER = 6,
    WH_MOUSE = 7,
    WH_HARDWARE = 8,
    WH_DEBUG = 9,
    WH_SHELL = 10,
    WH_FOREGROUNDIDLE = 11,
    WH_CALLWNDPROCRET = 12,
    WH_KEYBOARD_LL = 13,
    WH_MOUSE_LL = 14
  }

  #endregion

  #region Class LocalWindowsHook

  public class LocalWindowsHook
  {
    // ************************************************************************
    // Filter function delegate
    public delegate int HookProc(int code, IntPtr wParam, IntPtr lParam);

    // ************************************************************************

    // ************************************************************************
    // Internal properties
    protected IntPtr m_hhook = IntPtr.Zero;
    protected HookProc m_filterFunc;
    protected HookType m_hookType;
    // ************************************************************************
    // ReSharper restore InconsistentNaming

    // ************************************************************************
    // Event delegate
    public delegate void HookEventHandler(object sender, HookEventArgs e);

    // ************************************************************************

    // ************************************************************************
    // Event: HookInvoked 
    public event HookEventHandler HookInvoked;

    protected void OnHookInvoked(HookEventArgs e)
    {
      if (HookInvoked != null)
        HookInvoked(this, e);
    }

    // ************************************************************************

    // ************************************************************************
    // Class constructor(s)
    public LocalWindowsHook(HookType hook)
    {
      m_hookType = hook;
      m_filterFunc = new HookProc(CoreHookProc);
    }

    public LocalWindowsHook(HookType hook, HookProc func)
    {
      m_hookType = hook;
      m_filterFunc = func;
    }

    // ************************************************************************

    // ************************************************************************
    // Default filter function
    protected int CoreHookProc(int code, IntPtr wParam, IntPtr lParam)
    {
      if (code < 0)
        return CallNextHookEx(m_hhook, code, wParam, lParam);

      // Let clients determine what to do
      HookEventArgs e = new HookEventArgs {HookCode = code, wParam = wParam, lParam = lParam};
      OnHookInvoked(e);

      // Yield to the next hook in the chain
      return CallNextHookEx(m_hhook, code, wParam, lParam);
    }

    // ************************************************************************

    // ************************************************************************
    // Install the hook
    public void Install()
    {
      m_hhook = SetWindowsHookEx(
        m_hookType,
        m_filterFunc,
        IntPtr.Zero,
//       GetCurrentThreadId is obsolete, but the new version does not work 
//        Thread.CurrentThread.ManagedThreadId
#pragma warning disable 612,618
        AppDomain.GetCurrentThreadId()
#pragma warning restore 612,618
        );
    }

    // ************************************************************************

    // ************************************************************************
    // Uninstall the hook
    public void Uninstall()
    {
      UnhookWindowsHookEx(m_hhook);
    }

    // ************************************************************************

    #region Win32 Imports

    // ************************************************************************
    // Win32: SetWindowsHookEx()
    [DllImport("user32.dll")]
    protected static extern IntPtr SetWindowsHookEx(HookType code,
                                                    HookProc func,
                                                    IntPtr hInstance,
                                                    int threadID);

    // ************************************************************************

    // ************************************************************************
    // Win32: UnhookWindowsHookEx()
    [DllImport("user32.dll")]
    protected static extern int UnhookWindowsHookEx(IntPtr hhook);

    // ************************************************************************

    // ************************************************************************
    // Win32: CallNextHookEx()
    [DllImport("user32.dll")]
    protected static extern int CallNextHookEx(IntPtr hhook,
                                               int code, IntPtr wParam, IntPtr lParam);

    // ************************************************************************

    #endregion
  }

  #endregion
}