转载一篇关于 键盘 钩子的。。。代码。。。

using System;using System.Text;using System.Runtime.InteropServices;using System.Reflection;using System.Windows.Forms; namespace MouseKeyboardLibrary{     /// 
    /// Abstract base class for Mouse and Keyboard hooks    /// 
    public abstract class GlobalHook    {         #region Windows API Code         [StructLayout(LayoutKind.Sequential)]        protected class POINT        {            public int x;            public int y;        }         [StructLayout(LayoutKind.Sequential)]        protected class MouseHookStruct        {            public POINT pt;            public int hwnd;            public int wHitTestCode;            public int dwExtraInfo;        }         [StructLayout(LayoutKind.Sequential)]        protected class MouseLLHookStruct        {            public POINT pt;            public int mouseData;            public int flags;            public int time;            public int dwExtraInfo;        }         [StructLayout(LayoutKind.Sequential)]        protected class KeyboardHookStruct        {            public int vkCode;            public int scanCode;            public int flags;            public int time;            public int dwExtraInfo;        }         [DllImport("user32.dll", CharSet = CharSet.Auto,           CallingConvention = CallingConvention.StdCall, SetLastError = true)]        protected static extern int SetWindowsHookEx(            int idHook,            HookProc lpfn,            IntPtr hMod,            int dwThreadId);         [DllImport("user32.dll", CharSet = CharSet.Auto,            CallingConvention = CallingConvention.StdCall, SetLastError = true)]        protected static extern int UnhookWindowsHookEx(int idHook);          [DllImport("user32.dll", CharSet = CharSet.Auto,             CallingConvention = CallingConvention.StdCall)]        protected static extern int CallNextHookEx(            int idHook,            int nCode,            int wParam,            IntPtr lParam);         [DllImport("user32")]        protected static extern int ToAscii(            int uVirtKey,            int uScanCode,            byte[] lpbKeyState,            byte[] lpwTransKey,            int fuState);         [DllImport("user32")]        protected static extern int GetKeyboardState(byte[] pbKeyState);         [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]        protected static extern short GetKeyState(int vKey);         protected delegate int HookProc(int nCode, int wParam, IntPtr lParam);         protected const int WH_MOUSE_LL = 14;        protected const int WH_KEYBOARD_LL = 13;         protected const int WH_MOUSE = 7;        protected const int WH_KEYBOARD = 2;        protected const int WM_MOUSEMOVE = 0x200;        protected const int WM_LBUTTONDOWN = 0x201;        protected const int WM_RBUTTONDOWN = 0x204;        protected const int WM_MBUTTONDOWN = 0x207;        protected const int WM_LBUTTONUP = 0x202;        protected const int WM_RBUTTONUP = 0x205;        protected const int WM_MBUTTONUP = 0x208;        protected const int WM_LBUTTONDBLCLK = 0x203;        protected const int WM_RBUTTONDBLCLK = 0x206;        protected const int WM_MBUTTONDBLCLK = 0x209;        protected const int WM_MOUSEWHEEL = 0x020A;        protected const int WM_KEYDOWN = 0x100;        protected const int WM_KEYUP = 0x101;        protected const int WM_SYSKEYDOWN = 0x104;        protected const int WM_SYSKEYUP = 0x105;         protected const byte VK_SHIFT = 0x10;        protected const byte VK_CAPITAL = 0x14;        protected const byte VK_NUMLOCK = 0x90;         protected const byte VK_LSHIFT = 0xA0;        protected const byte VK_RSHIFT = 0xA1;        protected const byte VK_LCONTROL = 0xA2;        protected const byte VK_RCONTROL = 0x3;        protected const byte VK_LALT = 0xA4;        protected const byte VK_RALT = 0xA5;         protected const byte LLKHF_ALTDOWN = 0x20;         #endregion         #region Private Variables         protected int _hookType;        protected int _handleToHook;        protected bool _isStarted;        protected HookProc _hookCallback;         #endregion         #region Properties         public bool IsStarted        {            get            {                return _isStarted;            }        }         #endregion         #region Constructor         public GlobalHook()        {             Application.ApplicationExit += new EventHandler(Application_ApplicationExit);         }         #endregion         #region Methods         public void Start()        {             if (!_isStarted &&                _hookType != 0)            {                 // Make sure we keep a reference to this delegate!                // If not, GC randomly collects it, and a NullReference exception is thrown                _hookCallback = new HookProc(HookCallbackProcedure);                 _handleToHook = SetWindowsHookEx(                    _hookType,                    _hookCallback,                    Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly().GetModules()[0]),                    0);                 // Were we able to sucessfully start hook?                if (_handleToHook != 0)                {                    _isStarted = true;                }             }         }         public void Stop()        {             if (_isStarted)            {                 UnhookWindowsHookEx(_handleToHook);                 _isStarted = false;             }         }         protected virtual int HookCallbackProcedure(int nCode, Int32 wParam, IntPtr lParam)        {                        // This method must be overriden by each extending hook            return 0;         }         protected void Application_ApplicationExit(object sender, EventArgs e)        {             if (_isStarted)            {                Stop();            }         }         #endregion     } }