鍵盤事件偵測遮蔽熱鍵

事件偵測(hook)是Windows消息處理機制的一個平台，應用程式可以在上面設定子進程以監視指定視窗的某種消息， 而且所監視的視窗可以是其他進程所新增的，當消息到達後，在目標視窗處理函式之前處理它。 事件偵測機制允許應用程式截獲處理Windows消息或特定事件。 本範例透過事件偵測來遮蔽指定的系統快速鍵(如 Alt+F4 等)。

private IntPtr pKeyboardHook = IntPtr.Zero;                               //鍵盤事件偵測控制碼
public delegate int HookProc(int nCode, Int32 wParam, IntPtr lParam);     //事件偵測委託宣告
private HookProc KeyboardHookProcedure;                                   //鍵盤事件偵測委託範例不能省略變數
public const int idHook = 13;                                             //底層鍵盤事件偵測

[DllImport("user32.dll",CallingConvention = CallingConvention.StdCall)]   //安裝事件偵測函數
public static extern IntPtr SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr pInstance, int threadId);

[DllImport("user32.dll",CallingConvention = CallingConvention.StdCall)]   //卸載事件偵測函數
public static extern bool UnhookWindowsHookEx(IntPtr pHookHandle);

private int KeyboardHookProc(int nCode, Int32 wParam, IntPtr lParam)      //鍵盤事件偵測處理函數
{
    KeyMSG m = (KeyMSG)Marshal.PtrToStructure(lParam, typeof(KeyMSG));
    if(pKeyboardHook != IntPtr.Zero)
    {
        switch(((Keys)m.vkCode))
        {
            case Keys.LWin:
            case Keys.RWin:
            case Keys.Delete:
            case Keys.Alt:
            case Keys.Escape:
            case Keys.F4:
            case Keys.Control:
            case Keys.Tab:
                return 1;
        }
    }
    return 0;
}

public bool InsertHook()                                                 //自訂一個安裝事件偵測的方法
{
    IntPtr pIn = (IntPtr)4194304;
    if(this.pKeyboardHook == IntPtr.Zero)                                //如果沒有安裝偵測事件
    {
        this.KeyboardHookProcedure = new HookProc(KeyboardHookProc);
        this.pKeyboardHook = SetWindowHookEx(idHook, KeyboardHookProcedure, pIn, 0);  //安裝事件偵測
        if(this.pKeyboardHook == IntPtr.Zero)                            //如果安裝事件偵測失敗
        {
            this.UnInsertHook();                                         //卸載事件偵測
            return false;
        }
    }
    return true;                                                         //如果安裝成功則返回true
}

public bool UnInsertHook()                                               //自訂一個卸載事件偵測的方法
{
    bool result = true;
    if(this.pKeyboardHook != IntPtr.Zero)                                //如果存在鍵盤事件偵測
    {
        result = (UnhookWindowsHookEx(this.pKeyboardHook) && result);    //卸載事件偵測
        this.pKeyboardHook = IntPtr.Zero;
    }
    return result;
}