今天，有个同事问我，怎样在C#中使用全局钩子？以前写的全局钩子都是用unmanaged C或C++写个DLL来实现，可大家都知道，C#是基于.Net Framework的，是managed，怎么实现全局钩子呢？于是开始到网上搜索，好不容易找到一篇，318804 - HOW TO: Set a Windows Hook in Visual C# .NET，里面详细的说明了如何使用鼠标钩子捕获鼠标的移动等，可是，它只能在Application里起作用，出了Application就没用了，就是说它还是没有实现全局钩子，而且文章结尾处说：“Global Hooks are not supported in the .NET Framework...”，这可怎么办呢？
别担心，办法总是有的，经过一番摸索以后，发现WH_KEYBORAD_LL和WH_MOUSE_LL这两个low-level的hook可以被安装成全局的，这就好办了，我们不妨用这两个low-level的hook替换掉WH_KEYBORAD和WH_MOUSE，于是开始测试。结果成功了，在C#里实现了全局钩子。
我们来看一下主要代码段。示例源码下载地址请访问我的网站:http://www.vczx.com/article/show.php?id=1672
首先倒入所需要的windows函数，主要有三个，SetWindowsHookEX用来安装钩子，UnhookWindowsHookEX用来卸载钩子以及CallNextHookEX用来将hook信息传递到链表中下一个hook处理过程。
[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall, SetLastError = true)] private static extern int SetWindowsHookEx( int idHook, HookProc lpfn, IntPtr hMod, int dwThreadId);[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall, SetLastError = true)] private static extern int UnhookWindowsHookEx(int idHook);[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)] private static extern int CallNextHookEx( int idHook, int nCode, int wParam, IntPtr lParam);下面是有关这两个low-level hook在Winuser.h中的定义：
/// <summary>
/// Windows NT/2000/XP: Installs a hook procedure that monitors low-level mouse input events.
/// </summary> private const int WH_MOUSE_LL = 14; /// <summary> /// Windows NT/2000/XP: Installs a hook procedure that monitors low-level keyboard input events. /// </summary> private const int WH_KEYBOARD_LL = 13;在安装全局钩子的时候，我们就要做替换了，将WH_MOUSE和WH_KEYBORAD分别换成WH_MOUSE_LL和WH_KEYBORAD_LL：
//install hook hMouseHook = SetWindowsHookEx( WH_MOUSE_LL, //原来是WH_MOUSE MouseHookProcedure, Marshal.GetHINSTANCE( Assembly.GetExecutingAssembly().GetModules()[0]), 0);//install hook hKeyboardHook = SetWindowsHookEx( WH_KEYBOARD_LL, //原来是WH_KEYBORAD KeyboardHookProcedure, Marshal.GetHINSTANCE( Assembly.GetExecutingAssembly().GetModules()[0]), 0); 这样替换了之后，我们就可以实现全局钩子了，而且，不需要写DLL。看一下程序运行情况：
下面是关于鼠标和键盘的两个Callback函数：
private int MouseHookProc(int nCode, int wParam, IntPtr lParam) {
// if ok and someone listens to our events if ((nCode >= 0) && (OnMouseActivity != null))
{
//Marshall the data from callback. MouseLLHookStruct mouseHookStruct = (MouseLLHookStruct)Marshal.PtrToStructure(lParam, typeof(MouseLLHookStruct)); //detect button clicked MouseButtons button = MouseButtons.None; short mouseDelta = 0; switch (wParam) { case WM_LBUTTONDOWN: //case WM_LBUTTONUP: //case WM_LBUTTONDBLCLK: button = MouseButtons.Left; break; case WM_RBUTTONDOWN: //case WM_RBUTTONUP: //case WM_RBUTTONDBLCLK: button = MouseButtons.Right; break; case WM_MOUSEWHEEL: //If the message is WM_MOUSEWHEEL, the high-order word of mouseData member is the wheel delta. //One wheel click is defined as WHEEL_DELTA, which is 120. //(value >> 16) & 0xffff; retrieves the high-order word from the given 32-bit value mouseDelta = (short)((mouseHookStruct.mouseData >> 16) & 0xffff); //TODO: X BUTTONS (I havent them so was unable to test) //If the message is WM_XBUTTONDOWN, WM_XBUTTONUP, WM_XBUTTONDBLCLK, WM_NCXBUTTONDOWN, WM_NCXBUTTONUP, //or WM_NCXBUTTONDBLCLK, the high-order word specifies which X button was pressed or released, //and the low-order word is reserved. This value can be one or more of the following values. //Otherwise, mouseData is not used. break;
} //double clicks int clickCount = 0; if (button != MouseButtons.None) if (wParam == WM_LBUTTONDBLCLK || wParam == WM_RBUTTONDBLCLK) clickCount = 2; else clickCount = 1; //generate event MouseEventArgs e = new MouseEventArgs( button, clickCount, mouseHookStruct.pt.x, mouseHookStruct.pt.y, mouseDelta); //raise it OnMouseActivity(this, e); } //call next hook return CallNextHookEx(hMouseHook, nCode, wParam, lParam); }private int KeyboardHookProc(int nCode, Int32 wParam, IntPtr lParam) { //indicates if any of underlaing events set e.Handled flag bool handled = false; //it was ok and someone listens to events if ((nCode >= 0) && (KeyDown != null || KeyUp != null || KeyPress != null)) { //read structure KeyboardHookStruct at lParam KeyboardHookStruct MyKeyboardHookStruct = (KeyboardHookStruct)Marshal.PtrToStructure(lParam, typeof(KeyboardHookStruct)); //raise KeyDown if (KeyDown != null && (wParam == WM_KEYDOWN || wParam == WM_SYSKEYDOWN)) { Keys keyData = (Keys)MyKeyboardHookStruct.vkCode; KeyEventArgs e = new KeyEventArgs(keyData); KeyDown(this, e); handled = handled || e.Handled; } // raise KeyPress if (KeyPress != null && wParam == WM_KEYDOWN) { bool isDownShift = ((GetKeyState(VK_SHIFT) & 0x80) == 0x80 ? true : false); bool isDownCapslock = (GetKeyState(VK_CAPITAL) != 0 ? true : false); byte[] keyState = new byte[256]; GetKeyboardState(keyState); byte[] inBuffer = new byte[2]; if (ToAscii(MyKeyboardHookStruct.vkCode, MyKeyboardHookStruct.scanCode, keyState, inBuffer, MyKeyboardHookStruct.flags) == 1) { char key = (char)inBuffer[0]; if ((isDownCapslock ^ isDownShift) && Char.IsLetter(key)) key = Char.ToUpper(key); KeyPressEventArgs e = new KeyPressEventArgs(key); KeyPress(this, e); handled = handled || e.Handled; } } // raise KeyUp if (KeyUp != null && (wParam == WM_KEYUP || wParam == WM_SYSKEYUP)) { Keys keyData = (Keys)MyKeyboardHookStruct.vkCode; KeyEventArgs e = new KeyEventArgs(keyData); KeyUp(this, e); handled = handled || e.Handled; } } //if event handled in application do not handoff to other listeners if (handled) return 1; else return CallNextHookEx(hKeyboardHook, nCode, wParam, lParam); }参考资料：MSDN