如何在C#中使用全局鼠标、键盘Hook

　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。

[align=left][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);[/align]

[align=left]
　　下面是有关这两个low-level hook在Winuser.h中的定义：

[/align]

[align=left] private const int WH_MOUSE_LL = 14;
private const int WH_KEYBOARD_LL = 13;[/align]

[align=left]
　　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：

[/align]

[align=left]//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);[/align]

[align=left] [/align]
[align=left]　　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：

[/align]
[align=left]private int MouseHookProc(int nCode, int wParam, IntPtr lParam)
[/align]

[align=left] [/align]

[align=left]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);
}[/align]