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。
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> [Page]
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); [Page]
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; [Page]
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, [Page]
//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;
}