.NET 5 WPF全局低级键盘钩子触发ExecutionEngineException崩溃如何解决

问题根因 #

崩溃的核心原因是托管回调委托被GC意外回收。
你调用SetWindowsHookEx时直接传入Handler方法，编译器会隐式生成一个LowLevelKeyboardProc委托实例，但这个实例没有被你的代码持有任何强引用，GC执行回收时会直接清理该无引用的委托。后续系统触发钩子回调时，会访问已被释放的托管内存，最终触发ExecutionEngineException异常。

修复方案 #

1. 将回调委托作为类的成员变量显式持有，避免GC回收
2. 补充钩子卸载逻辑，避免资源泄漏

修复后的完整代码 #

public partial class MainWindow : Window {
    private const int WH_KEYBOARD_LL = 13;
    private const int WM_KEYDOWN = 0x0100;
    private const int WM_SYSKEYDOWN = 0x0104;

    private delegate IntPtr LowLevelKeyboardProc(int nCode, IntPtr wParam, IntPtr lParam);

    // 显式持有委托实例，防止GC回收
    private LowLevelKeyboardProc _keyboardProc;

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr SetWindowsHookEx(int idHook, LowLevelKeyboardProc lpfn, IntPtr hMod,
        uint dwThreadId);

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode,
        IntPtr wParam, IntPtr lParam);
    
    [DllImport("kernel32", SetLastError = true, CharSet = CharSet.Ansi)]
    static extern IntPtr LoadLibrary([MarshalAs(UnmanagedType.LPStr)] string lpFileName);

    // 补充卸载钩子的API
    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern bool UnhookWindowsHookEx(IntPtr hhk);

    private IntPtr _hook;


    public bool Hook() {
        if (_hook == IntPtr.Zero) {
            // 先给成员委托赋值，再传入API
            _keyboardProc = Handler;
            var modPtr = LoadLibrary("user32.dll");
            _hook = SetWindowsHookEx(WH_KEYBOARD_LL, _keyboardProc, modPtr, 0);
        }
        return _hook != IntPtr.Zero;
    }

    private IntPtr Handler(int code, IntPtr param, IntPtr lParam) {
        return CallNextHookEx(_hook, code, param, lParam);
    }

    public MainWindow() {
        InitializeComponent();
        Hook();
        // 窗口关闭时卸载钩子
        Closing += (s, e) => {
            if (_hook != IntPtr.Zero) {
                UnhookWindowsHookEx(_hook);
                _hook = IntPtr.Zero;
            }
        };
    }
}

修改后可稳定复现的崩溃问题会完全消失，快速多次按键也不会再触发异常。

内容的提问来源于stack exchange，提问作者CShark