相信以前用过VB、Delphi，特别是VC的程序员应该对钩子程序都不陌生。在C#中我们同样可以使用钩子程序来实现特殊效果，比如当用户按下某个特殊键时提示，比如关闭应用程序前提示等。
当然使用方法相对VC来说要稍微复杂一点，有的地方还不太方便，下面的例子中实现两个基本功能：
1、按下Alt+F4时使窗口最小化
2、关闭应用程序前提示
不过目前只能捕获消息，不能屏蔽消息，我正在实验，也希望知道的高手能多多指教
一、加入winuser.h中的定义
因为钩子程序一般情况下都是在vc下使用的，在c#里面并没有对应的方法、结构等的定义，我们首先需要把winuser.h中的相关定义加入自己的类
public enum HookType : int
{
WH_JOURNALRECORD = 0,
WH_JOURNALPLAYBACK = 1,
WH_KEYBOARD = 2,
WH_GETMESSAGE = 3,
WH_CALLWNDPROC = 4,
WH_CBT = 5,
WH_SYSMSGFILTER = 6,
WH_MOUSE = 7,
WH_HARDWARE = 8,
WH_DEBUG = 9,
WH_SHELL = 10,
WH_FOREGROUNDIDLE = 11,
WH_CALLWNDPROCRET = 12,
WH_KEYBOARD_LL = 13,
WH_MOUSE_LL = 14
}具体的说明在msdn中都可以查到，主要的比如WH_KEYBOARD是监控按键事件，WH_CALLWNDPROC是在消息触发时执行
public enum VirtualKeys
{
VK_SHIFT = 0x10,
VK_CONTROL = 0x11,
VK_MENU = 0x12, //ALT
VK_PAUSE = 0x13,
VK_CAPITAL = 0x14
}这个不用说明了，对应ALT、CTRL等键
public struct CWPSTRUCT
{
public IntPtr lparam;
public IntPtr wparam;
public int message;
public IntPtr hwnd;
}这个是windows内部传递过来的消息的结构
二、加入自己定义的委托和事件参数
public delegate int HookProc(int code, IntPtr wParam, IntPtr lParam);
public delegate void HookEventHandler(object sender, HookEventArgs e);
HokkProc是
SetWindowsHookEx调用时的委托事件，HookEventHandler是自己的委托事件
public class HookEventArgs : EventArgs
{
public int HookCode;
public IntPtr wParam;
public IntPtr lParam;
public Keys key;
public bool bAltKey;
public bool bCtrlKey;
}是自己的委托事件中接受的事件参数
三、实现自己的钩子类这一步是最重要的，要使用钩子，我们需要引用
user32.dll中的相应方法：
[DllImport("user32.dll")]
static extern IntPtr SetWindowsHookEx(HookType hook, HookProc callback, IntPtr hMod, uint dwThreadId);
[DllImport("user32.dll")]
static extern bool UnhookWindowsHookEx(IntPtr hhk);
[DllImport("user32.dll")]
static extern int CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam);
[DllImport("user32.dll")]
static extern short GetKeyState(VirtualKeys nVirtKey);
SetWindowsHookEx是注册一个钩子程序，
UnhookWindowsHookEx是释放钩子程序，
CallNextHookEx调用钩子的后续事件处理，
GetKeyState得到所按的虚键
然后就可以调用这些方法来实现钩子程序，比如注册一个钩子可以调用：
m_hook = SetWindowsHookEx(m_hooktype, m_hookproc, IntPtr.Zero, (uint)AppDomain.GetCurrentThreadId());
其中m_hooktype就是
HookType中定义的类型，m_hookproc就是实际的钩子处理程序：
m_hookproc = new HookProc(KeyHookProcedure); 最关键的就是
KeyHookProcedure等钩子处理程序：
protected int KeyHookProcedure(int code, IntPtr wParam, IntPtr lParam)
{
if (code != 0)
{
return CallNextHookEx(m_hook, code, wParam, lParam);
}
if (HookInvoked != null)
{
Keys key = (Keys)wParam.ToInt32();
HookEventArgs eventArgs = new HookEventArgs();
eventArgs.key = key;
eventArgs.lParam = lParam;
eventArgs.wParam = wParam;
eventArgs.HookCode = code;
eventArgs.bAltKey = GetKeyState(VirtualKeys.VK_MENU) <= -127;
eventArgs.bCtrlKey = GetKeyState(VirtualKeys.VK_CONTROL) <= -127;
HookInvoked(this, eventArgs);
}
return CallNextHookEx(m_hook, code, wParam, lParam);
} 在这个事件中可以取得消息的参数，特别是按键的值，然后通过HookInvoked委托调用事件实际的处理程序
四、在应用程序中调用钩子类
我们可以在自己的form中声明两个钩子对象
private MyHook callProcHook = new MyHook(HookType.WH_CALLWNDPROC);
private MyHook keyHook = new MyHook(HookType.WH_KEYBOARD);
然后在初始化时注册钩子：
private void Form1_Load(object sender, EventArgs e)
{
keyHook.HookInvoked += new HookEventHandler(keyHook_HookInvoked);
keyHook.Install();
callProcHook.HookInvoked += new HookEventHandler(callProcHook_HookInvoked);
callProcHook.Install();
} 然后就是实际的钩子事件：
private void keyHook_HookInvoked(object sender, HookEventArgs e)
{
if (e.key == Keys.F4 && e.bAltKey) //Alt + F4
{
this.WindowState = FormWindowState.Minimized;
}
}
private void callProcHook_HookInvoked(object sender, HookEventArgs e)
{
unsafe
{
CWPSTRUCT* message = (CWPSTRUCT*)e.lParam;
if (message != null)
{
if (message->message == WM_CLOSE)
{
(sender as MyHook).CallNextProc = false;
MessageBox.Show("程序即将关闭！");
}
}
}
} 这样我们就可以通过钩子实现一些相对底层的应用。
代码说的有点乱，我就把最主要的代码直接列在下面供大家参考：
1using System;
2using System.Collections.Generic;
3using System.ComponentModel;
4using System.Data;
5using System.Drawing;
6using System.Text;
7using System.Windows.Forms;
8using System.Runtime.InteropServices;
9
10namespace HookTest
11{
12 public partial class Form1 : Form
13 {
14 消息定义(WinUser.h中定义)#region 消息定义(WinUser.h中定义)
15 private const int WM_PAINT = 0x000F;
16 private const int WM_CLOSE = 0x0010;
17 private const int WM_QUIT = 0x0012;
18 private const int WM_DESTROY = 0x0002;
19 #endregion
20
21 private MyHook callProcHook = new MyHook(HookType.WH_CALLWNDPROC);
22 private MyHook keyHook = new MyHook(HookType.WH_KEYBOARD);
23
24 public Form1()
25 {
26 InitializeComponent();
27 }
28
29 private void Form1_Load(object sender, EventArgs e)
30 {
31 keyHook.HookInvoked += new HookEventHandler(keyHook_HookInvoked);
32 keyHook.Install();
33
34 callProcHook.HookInvoked += new HookEventHandler(callProcHook_HookInvoked);
35 callProcHook.Install();
36 }
37
38 private void keyHook_HookInvoked(object sender, HookEventArgs e)
39 {
40 if (e.key == Keys.F4 && e.bAltKey) //Alt + F4
41 {
42 this.WindowState = FormWindowState.Minimized;
43 }
44 }
45
46 private void callProcHook_HookInvoked(object sender, HookEventArgs e)
47 {
48 unsafe
49 {
50 CWPSTRUCT* message = (CWPSTRUCT*)e.lParam;
51 if (message != null)
52 {
53 if (message->message == WM_CLOSE)
54 {
55 (sender as MyHook).CallNextProc = false;
56 MessageBox.Show("程序即将关闭！");
57 }
58 }
59 }
60 }
61
62 }
63
64 消息结构体(参照WinUser.h中定义)#region 消息结构体(参照WinUser.h中定义)
65 public struct CWPSTRUCT
66 {
67 public IntPtr lparam;
68 public IntPtr wparam;
69 public int message;
70 public IntPtr hwnd;
71 }
72 #endregion
73
74 钩子类型的枚举#region 钩子类型的枚举
75 public enum HookType : int
76 {
77 WH_JOURNALRECORD = 0,
78 WH_JOURNALPLAYBACK = 1,
79 WH_KEYBOARD = 2,
80 WH_GETMESSAGE = 3,
81 WH_CALLWNDPROC = 4,
82 WH_CBT = 5,
83 WH_SYSMSGFILTER = 6,
84 WH_MOUSE = 7,
85 WH_HARDWARE = 8,
86 WH_DEBUG = 9,
87 WH_SHELL = 10,
88 WH_FOREGROUNDIDLE = 11,
89 WH_CALLWNDPROCRET = 12,
90 WH_KEYBOARD_LL = 13,
91 WH_MOUSE_LL = 14
92 }
93 #endregion
94
95 虚键值的定义(参照WinUser.h中定义)#region 虚键值的定义(参照WinUser.h中定义)
96 public enum VirtualKeys
97 {
98 VK_SHIFT = 0x10,
99 VK_CONTROL = 0x11,
100 VK_MENU = 0x12, //ALT
101 VK_PAUSE = 0x13,
102 VK_CAPITAL = 0x14
103 }
104 #endregion
105
106 钩子委托#region 钩子委托
107 public delegate int HookProc(int code, IntPtr wParam, IntPtr lParam);
108 public delegate void HookEventHandler(object sender, HookEventArgs e);
109 #endregion
110
111 钩子事件参数#region 钩子事件参数
112 public class HookEventArgs : EventArgs
113 {
114 public int HookCode;
115 public IntPtr wParam;
116 public IntPtr lParam;
117 public Keys key;
118 public bool bAltKey;
119 public bool bCtrlKey;
120 }
121 #endregion
122
123 钩子类#region 钩子类
124 public class MyHook
125 {
126 调用Windows API#region 调用Windows API
127 [DllImport("user32.dll")]
128 static extern IntPtr SetWindowsHookEx(HookType hook, HookProc callback, IntPtr hMod, uint dwThreadId);
129
130 [DllImport("user32.dll")]
131 static extern bool UnhookWindowsHookEx(IntPtr hhk);
132
133 [DllImport("user32.dll")]
134 static extern int CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam);
135
136 [DllImport("user32.dll")]
137 static extern short GetKeyState(VirtualKeys nVirtKey);
138 #endregion
139
140 局部变量#region 局部变量
141 private IntPtr m_hook;
142 private HookType m_hooktype;
143 private HookProc m_hookproc;
144
145 private bool _bCallNext;
146
147 public bool CallNextProc
148 {
149 get { return _bCallNext; }
150 set { _bCallNext = value; }
151 }
152
153 #endregion
154
155 public event HookEventHandler HookInvoked;
156
157 public void Install()
158 {
159 m_hook = SetWindowsHookEx(m_hooktype, m_hookproc, IntPtr.Zero, (uint)AppDomain.GetCurrentThreadId());
160 }
161
162 public void Uninstall()
163 {
164 if (m_hook != IntPtr.Zero)
165 {
166 UnhookWindowsHookEx(m_hook);
167 }
168 }
169
170 public MyHook(HookType HookType)
171 {
172 m_hooktype = HookType;
173 if (m_hooktype == HookType.WH_KEYBOARD)
174 {
175 m_hookproc = new HookProc(KeyHookProcedure);
176 }
177 else if (m_hooktype == HookType.WH_CALLWNDPROC)
178 {
179 m_hookproc = new HookProc(CallProcHookProcedure);
180 }
181 }
182
183 protected int KeyHookProcedure(int code, IntPtr wParam, IntPtr lParam)
184 {
185 if (code != 0)
186 {
187 return CallNextHookEx(m_hook, code, wParam, lParam);
188 }
189
190 if (HookInvoked != null)
191 {
192 Keys key = (Keys)wParam.ToInt32();
193 HookEventArgs eventArgs = new HookEventArgs();
194 eventArgs.key = key;
195 eventArgs.lParam = lParam;
196 eventArgs.wParam = wParam;
197 eventArgs.HookCode = code;
198 eventArgs.bAltKey = GetKeyState(VirtualKeys.VK_MENU) <= -127;
199 eventArgs.bCtrlKey = GetKeyState(VirtualKeys.VK_CONTROL) <= -127;
200 HookInvoked(this, eventArgs);
201 }
202
203 return CallNextHookEx(m_hook, code, wParam, lParam);
204 }
205
206 protected int CallProcHookProcedure(int code, IntPtr wParam, IntPtr lParam)
207 {
208 try
209 {
210 CallNextProc = true;
211 if (HookInvoked != null)
212 {
213 HookEventArgs eventArgs = new HookEventArgs();
214 eventArgs.lParam = lParam;
215 eventArgs.wParam = wParam;
216 eventArgs.HookCode = code;
217 HookInvoked(this, eventArgs);
218 }
219
220 if (CallNextProc)
221 {
222 return CallNextHookEx(m_hook, code, wParam, lParam);
223 }
224 else
225 {
226 //return 1;
227 return CallNextHookEx(IntPtr.Zero, code, wParam, lParam);
228 }
229 }
230 catch (Exception ex)
231 {
232 MessageBox.Show(ex.Message);
233 return 0;
234 }
235 }
236 }
237 #endregion
238}
以上的钩子只对当前应用程序起作用，如果想控制其他的所有程序，需要使用全局钩子。原则上全局钩子在C#中是不支持的，在http://www.codeproject.com/csharp/globalhook.asp 中的代码可以参照来实现全局钩子
