使用钩子函数屏蔽特殊功能键为什么屏蔽不了Alt+Ctrl+Delete
代码如下:(粗体部分)
public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        public delegate int HookProc(int nCode, int wParam, IntPtr lParam);

        static int hHook = 0;

        public const int WH_KEYBOARD_LL = 13;
        //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;
        }

        //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)
        &n