C#做勾子程序怎么实现！？？？

Question

1.勾子程序有几种功能是什么？
2.用C#实现一个简单的勾子程序要原码，能直接在vs里面直接运行的多谢

Answer 1

1.勾子程序有几种功能是什么？
2.用C#实现一个简单的勾子程序要原码，能直接在vs里面直接运行的
口气像面试官，可惜我不是来面试的

Answer 2

 #region 键盘钩子
        public delegate int HookProc(int nCode, int wParam, IntPtr lParam);
        static int hHook = 0;
        public const int WH_KEYBOARD_LL = 13;        public int startindex = -1;        //LowLevel键盘截获，如果是WH_KEYBOARD＝2，并不能对系统键盘截取，Acrobat Reader会在你截取之前获得键盘。  
        HookProc KeyBoardHookProcedure;        //键盘Hook结构函数  
        [StructLayout(LayoutKind.Sequential)]
        public class KeyBoardHookStruct
        {
            public int vkCode;
            public int scanCode;
            public int flags;
            public int time;
            public int dwExtraInfo;
        }
        #region DllImport
        //设置钩子  
        [DllImport("user32.dll")]
        public static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);
        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        //抽掉钩子  
        public static extern bool UnhookWindowsHookEx(int idHook);
        [DllImport("user32.dll")]
        //调用下一个钩子  
        public static extern int CallNextHookEx(int idHook, int nCode, int wParam, IntPtr lParam);        [DllImport("kernel32.dll")]
        public static extern int GetCurrentThreadId();        [DllImport("kernel32.dll")]
        public static extern IntPtr GetModuleHandle(string name);        public void Hook_Start()
        {
            // 安装键盘钩子  
            if (hHook == 0)
            {
                KeyBoardHookProcedure = new HookProc(KeyBoardHookProc);                //hHook = SetWindowsHookEx(2,  
                // KeyBoardHookProcedure,  
                // GetModuleHandle(Process.GetCurrentProcess().MainModule.ModuleName), GetCurrentThreadId());                  hHook = SetWindowsHookEx(WH_KEYBOARD_LL,
                KeyBoardHookProcedure,
                GetModuleHandle(Process.GetCurrentProcess().MainModule.ModuleName), 0);                //如果设置钩子失败.  
                if (hHook == 0)
                {
                    Hook_Clear();
                    //throw new Exception("设置Hook失败!");  
                }
            }
        }        //取消钩子事件  
        public void Hook_Clear()
        {
            bool retKeyboard = true;
            if (hHook != 0)
            {
                retKeyboard = UnhookWindowsHookEx(hHook);
                hHook = 0;
            }
            //如果去掉钩子失败.  
            if (!retKeyboard) throw new Exception("UnhookWindowsHookEx failed.");
        }
        public int KeyBoardHookProc(int nCode, int wParam, IntPtr lParam)
         {
            if (nCode >= 0)
            {
                KeyBoardHookStruct kbh = (KeyBoardHookStruct)Marshal.PtrToStructure(lParam, typeof(KeyBoardHookStruct));
                if (kbh.vkCode == 32)  //空格
                {
                    int estrat = 0;
                    int eend = 0;
                    int etype = -1;  //简单元素类型：0选择类，1是输入框，2是诊断类
                    if (richTextBox1.ReadOnly == false)
                    {
                        int inde = 0;
                        try
                        {
                            inde = richTextBox1.SelectionStart;
                        }
                        catch (Exception)
                        {                            inde = 0;
                            Hook_Clear();
                        }
                        if (isInSelectElement(pageText, inde, ref estrat, ref eend, ref etype) == true && (etype == 0 || etype == 2))//在选择类型的简单元素中
                        {
                            startindex = richTextBox1.SelectionStart;
                            OnDoubleClick(null, null);              //在选择元素中空白时  效果等于双击
                            //                        }
                        else
                        {
                            Hook_Clear();
                        }
                    }
                    return 1;
                }
            }
            return CallNextHookEx(hHook, nCode, wParam, lParam);
        }        #endregion