调用Win32 API（优先级最高，全局监听， 支持最小化失焦等情况）

那么，假如我要在一个WPF程序监听CTRL+5按键，首先在主窗口程序添加以下代码：

        /// <summary>
        /// CTRL+5事件Id
        /// </summary>
        private const int Ctrl5KeyEventId = 9000;


        [DllImport("user32.dll")]
        public static extern bool RegisterHotKey(IntPtr hWnd, int id, uint fsModifiers, uint vk);

        [DllImport("user32.dll")]
        public static extern bool UnregisterHotKey(IntPtr hWnd, int id);


        protected override void OnSourceInitialized(EventArgs e)
        {
            base.OnSourceInitialized(e);

            var handle = new WindowInteropHelper(this).Handle;
            var source = HwndSource.FromHwnd(handle);
            source?.AddHook(HwndHook);
            //真正注册快捷键监听处理: 同时注册数字键和小键盘的CTRL+5
            RegisterHotKey(handle, Ctrl5KeyEventId, (uint)ModifierKeys.Control, (uint)KeyInterop.VirtualKeyFromKey(Key.D5));
            RegisterHotKey(handle, Ctrl5KeyEventId, (uint)ModifierKeys.Control, (uint)KeyInterop.VirtualKeyFromKey(Key.NumPad5));
        }


        private IntPtr HwndHook(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
        {
            const int wmHotkey = 0x0312;

            switch (msg)
            {
                case wmHotkey:
                    switch (wParam.ToInt32())
                    {
                        case Ctrl5KeyEventId:
                            Debug.WriteLine("Win32监听CTRL+5成功");
                            break;
                    }
                    break;
            }

            return IntPtr.Zero;
        }


        protected override void OnClosing(CancelEventArgs e)
        {
            base.OnClosing(e);

            var handle = new WindowInteropHelper(this).Handle;
            //关闭窗口后取消注册
            UnregisterHotKey(handle, Ctrl5KeyEventId);
        }

监听WPF的KeyDown事件（不够清真，可选择，最小化失焦等情况监听失效）

        public MainWindow()
        {
            InitializeComponent();
            KeyDown += MainWindow_KeyDown;
        }


        private void MainWindow_KeyDown(object sender, KeyEventArgs e)
        {
            if (Keyboard.Modifiers == ModifierKeys.Control && (e.Key == Key.D5 || e.Key == Key.NumPad5))
            {
                Debug.WriteLine("WPF的KeyDown事件监听CTRL+5成功"); ;
                e.Handled = true;
            }
        }

XAML绑定命令方式（WPF当然优先选中命令绑定啦，清真，最小化失焦等情况监听失效）

以下为Window主窗体的XAML代码

    <Window.CommandBindings>
        <CommandBinding Command="{x:Static local:Commands.Ctrl5Command}" Executed="Ctrl5Command_OnExecuted"/>
    </Window.CommandBindings>
    <Window.InputBindings>
        <KeyBinding Modifiers="Control" Key="D5"  Command="{x:Static  local:Commands.Ctrl5Command}" />
        <KeyBinding Modifiers="Control" Key="NumPad5"  Command="{x:Static  local:Commands.Ctrl5Command}" />
    </Window.InputBindings>

在Window主窗体后台代码创建命令对应的Executed方法

        private void Ctrl5Command_OnExecuted(object sender, ExecutedRoutedEventArgs e)
        {
            Debug.WriteLine("WPF的XAML绑定命令监听CTRL+5成功");
        }

新增命令相关的静态类：

    public static class Commands
    {
        public static ICommand Ctrl5Command { get; } = new RoutedCommand();
    }

细节

三个监听方案的优先级

其中Win32 > XAML绑定命令 = KeyDown事件,假如同时监听的话，其中会只处理高优先级的，以上面的例子，假如
我同时监听三个，只会处理win32的

Win32监听CTRL+5成功

全局监听问题

其中win32支持全局监听键盘，也就是窗口在失焦情况下，例如最小化，也能监听得到，其中XAML绑定命令和KeyDown事件不支持失焦情况，最小化等情况也就监听不到了，因此，要按业务选择方案

DEMO

DEMO链接