C# hook的一个简单例子

效果是：你输入“b”，它肯定还是“a”。。。-_-!!!

public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

internal enum HookType //枚举，钩子的类型
{
//MsgFilter = -1,
//JournalRecord = 0,
//JournalPlayback = 1,
Keyboard = 2,
//GetMessage = 3,
//CallWndProc = 4,
//CBT = 5,
//SysMsgFilter = 6,

//Mouse = 7,
//Hardware = 8,
//Debug = 9,
//Shell = 10,
//ForegroundIdle = 11,
//CallWndProcRet = 12,
//KeyboardLL = 13,
//MouseLL = 14,
};

IntPtr _nextHookPtr; //记录Hook编号

[DllImport("kernel32.dll")]
static extern int GetCurrentThreadId(); //取得当前线程编号的API

[DllImport("User32.dll")]
internal extern static void UnhookWindowsHookEx(IntPtr handle); //取消Hook的API

[DllImport("User32.dll")]
internal extern static IntPtr SetWindowsHookEx(int idHook, [MarshalAs(UnmanagedType.FunctionPtr)] HookProc lpfn, IntPtr hinstance, int threadID); //设置Hook的API

[DllImport("User32.dll")]
internal extern static IntPtr CallNextHookEx(IntPtr handle, int code, IntPtr wparam, IntPtr lparam); //取得下一个Hook的API

internal delegate IntPtr HookProc(int code, IntPtr wparam, IntPtr lparam);

IntPtr MyHookProc(int code, IntPtr wparam, IntPtr lparam)
{
if (code < 0) return CallNextHookEx(_nextHookPtr, code, wparam, lparam); //返回，让后面的程序处理该消息
if (wparam.ToInt32() == 98 || wparam.ToInt32() == 66) //如果用户输入的是 b
{
this.textBox1.Text += "a";
return (IntPtr)1; //直接返回了，该消息就处理结束了
}
else
{
return IntPtr.Zero; //返回，让后面的程序处理该消息
}
}
public void SetHook()
{
if (_nextHookPtr != IntPtr.Zero) //已经勾过了
return;

HookProc myhookProc = new HookProc(MyHookProc); //声明一个自己的Hook实现函数的委托对象

_nextHookPtr = SetWindowsHookEx((int)HookType.Keyboard, myhookProc, IntPtr.Zero, GetCurrentThreadId()); //加到Hook链中
}

public void UnHook()
{
if (_nextHookPtr != IntPtr.Zero)
{
UnhookWindowsHookEx(_nextHookPtr); //从Hook链中取消
_nextHookPtr = IntPtr.Zero;
}
}

private void Form1_Load(object sender, EventArgs e)
{
SetHook();
}

private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
UnHook();
}

}

【THX 4 the Code from ALAN (a C# programmer) /article/7014921.html】

【Microsoft 对 hook 的解读：http://www.microsoft.com/china/community/program/originalarticles/techdoc/hook.mspx】