How do you check if a shortcut was pressed using c#?

Question

I want to make an app hide itself if a shortcut was pressed (ex: Alt + Shift + Z), and then show itself if a different shortcut was pressed. However, I do not know how to figure out if multiple keys were pressed. Thanks in advance.

Answer 1

@Morgenstern, Welcome to Microsoft Q&A, I recommend that you could try to use windows api RegisterHotKey function to register the hot key and then use the HotKeyPressed event to check if the combinations keys are pressed.

Here is a code example in windows form app:

using System;
using System.Runtime.InteropServices;
using System.Threading;
using System.Windows.Forms;






public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        
        private void Form1_Load(object sender, EventArgs e)
        {
            HotKeyManager.RegisterHotKey(Keys.Z, KeyModifiers.Alt|KeyModifiers.Shift);
            HotKeyManager.HotKeyPressed += new EventHandler<HotKeyEventArgs>(HotKeyManager_HotKeyPressed);
        }
         void HotKeyManager_HotKeyPressed(object sender, HotKeyEventArgs e)
        {
            this.Invoke(new MethodInvoker(this.Hide));
        }

    }

    public static class HotKeyManager
    {
        public static event EventHandler<HotKeyEventArgs> HotKeyPressed;

        public static int RegisterHotKey(Keys key, KeyModifiers modifiers)
        {
            _windowReadyEvent.WaitOne();
            int id = System.Threading.Interlocked.Increment(ref _id);
            _wnd.Invoke(new RegisterHotKeyDelegate(RegisterHotKeyInternal), _hwnd, id, (uint)modifiers, (uint)key);
            return id;
        }

        public static void UnregisterHotKey(int id)
        {
            _wnd.Invoke(new UnRegisterHotKeyDelegate(UnRegisterHotKeyInternal), _hwnd, id);
        }

        delegate void RegisterHotKeyDelegate(IntPtr hwnd, int id, uint modifiers, uint key);
        delegate void UnRegisterHotKeyDelegate(IntPtr hwnd, int id);

        private static void RegisterHotKeyInternal(IntPtr hwnd, int id, uint modifiers, uint key)
        {
            RegisterHotKey(hwnd, id, modifiers, key);
        }

        private static void UnRegisterHotKeyInternal(IntPtr hwnd, int id)
        {
            UnregisterHotKey(_hwnd, id);
        }

        private static void OnHotKeyPressed(HotKeyEventArgs e)
        {
            if (HotKeyManager.HotKeyPressed != null)
            {
                HotKeyManager.HotKeyPressed(null, e);
            }
        }

        private static volatile MessageWindow _wnd;
        private static volatile IntPtr _hwnd;
        private static ManualResetEvent _windowReadyEvent = new ManualResetEvent(false);
        static HotKeyManager()
        {
            Thread messageLoop = new Thread(delegate ()
            {
                Application.Run(new MessageWindow());
            });
            messageLoop.Name = "MessageLoopThread";
            messageLoop.IsBackground = true;
            messageLoop.Start();
        }

        private class MessageWindow : Form
        {
            public MessageWindow()
            {
                _wnd = this;
                _hwnd = this.Handle;
                _windowReadyEvent.Set();
            }

            protected override void WndProc(ref Message m)
            {
                if (m.Msg == WM_HOTKEY)
                {
                    HotKeyEventArgs e = new HotKeyEventArgs(m.LParam);
                    HotKeyManager.OnHotKeyPressed(e);
                }

                base.WndProc(ref m);
            }

            protected override void SetVisibleCore(bool value)
            {
                // Ensure the window never becomes visible
                base.SetVisibleCore(false);
            }

            private const int WM_HOTKEY = 0x312;
        }

        [DllImport("user32", SetLastError = true)]
        private static extern bool RegisterHotKey(IntPtr hWnd, int id, uint fsModifiers, uint vk);

        [DllImport("user32", SetLastError = true)]
        private static extern bool UnregisterHotKey(IntPtr hWnd, int id);

        private static int _id = 0;
    }


    public class HotKeyEventArgs : EventArgs
    {
        public readonly Keys Key;
        public readonly KeyModifiers Modifiers;

        public HotKeyEventArgs(Keys key, KeyModifiers modifiers)
        {
            this.Key = key;
            this.Modifiers = modifiers;
        }

        public HotKeyEventArgs(IntPtr hotKeyParam)
        {
            uint param = (uint)hotKeyParam.ToInt64();
            Key = (Keys)((param & 0xffff0000) >> 16);
            Modifiers = (KeyModifiers)(param & 0x0000ffff);
        }
    }

    [Flags]
    public enum KeyModifiers
    {
        Alt = 1,
        Control = 2,
        Shift = 4,
        Windows = 8,
        NoRepeat = 0x4000
    }

Based on my test, it will hide the current form when you press Alt + Shift + Z.

Hope my solution could help you.

Best Regards,

Jack

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