Global hotkey for windowless app with NotifyIcon

Question

I have a windowless winforms application that uses an ApplicationContext to setup a NotifyIcon (TrayIcon) with which the user can control. But I also want to use hotkeys.

I found some good approaches using RegisterHotkey (eg. Global hotkeys in windowless .NET app), but they all need a form or a native window, which I don't want to use because of side-effects.

But I already use a NotifyIcon (TrayIcon) and I guess that has some kind of message pipe to trigger clicks etc. already. How can I use that one to register global hotkeys?

Answer 1

I required the same and finally I found this answer on another question Set global hotkeys using C# It is working perfectly with tray (NotifyIcon) application.

I am aligning the code for tray application, just follow the below steps:

1. Create new class "KeyboardHook"

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

namespace MyTrayApp
{
    public sealed class KeyboardHook : IDisposable
    {
        // Registers a hot key with Windows.
        [DllImport("user32.dll")]
        private static extern bool RegisterHotKey(IntPtr hWnd, int id, uint fsModifiers, uint vk);
        // Unregisters the hot key with Windows.
        [DllImport("user32.dll")]
        private static extern bool UnregisterHotKey(IntPtr hWnd, int id);

        /// <summary>
        /// Represents the window that is used internally to get the messages.
        /// </summary>
        private class Window : NativeWindow, IDisposable
        {
            private static int WM_HOTKEY = 0x0312;

            public Window()
            {
                // create the handle for the window.
                this.CreateHandle(new CreateParams());
            }

            /// <summary>
            /// Overridden to get the notifications.
            /// </summary>
            /// <param name="m"></param>
            protected override void WndProc(ref Message m)
            {
                base.WndProc(ref m);

                // check if we got a hot key pressed.
                if (m.Msg == WM_HOTKEY)
                {
                    // get the keys.
                    Keys key = (Keys)(((int)m.LParam >> 16) & 0xFFFF);
                    ModifierKeys modifier = (ModifierKeys)((int)m.LParam & 0xFFFF);

                    // invoke the event to notify the parent.
                    if (KeyPressed != null)
                        KeyPressed(this, new KeyPressedEventArgs(modifier, key));
                }
            }

            public event EventHandler<KeyPressedEventArgs> KeyPressed;

            #region IDisposable Members

            public void Dispose()
            {
                this.DestroyHandle();
            }

            #endregion
        }

        private Window _window = new Window();
        private int _currentId;

        public KeyboardHook()
        {
            // register the event of the inner native window.
            _window.KeyPressed += delegate (object sender, KeyPressedEventArgs args)
            {
                if (KeyPressed != null)
                    KeyPressed(this, args);
            };
        }

        /// <summary>
        /// Registers a hot key in the system.
        /// </summary>
        /// <param name="modifier">The modifiers that are associated with the hot key.</param>
        /// <param name="key">The key itself that is associated with the hot key.</param>
        public void RegisterHotKey(ModifierKeys modifier, Keys key)
        {
            // increment the counter.
            _currentId = _currentId + 1;

            // register the hot key.
            if (!RegisterHotKey(_window.Handle, _currentId, (uint)modifier, (uint)key))
            {
                string message = "The hotkey \"Ctrl+Alt+K\" could not be registered. This problem is probably causedby another tool claiming usage of the same hotkey!\r\n\r\nAll KeepOn features still work directly from the tray icon context menu without hotkey.";
                string title = "KeepOn";
                MessageBoxButtons buttons = MessageBoxButtons.OK;
                MessageBoxIcon icon = MessageBoxIcon.Exclamation;
                DialogResult result = MessageBox.Show(message, title, buttons,icon);
            }
        }

        /// <summary>
        /// A hot key has been pressed.
        /// </summary>
        public event EventHandler<KeyPressedEventArgs> KeyPressed;

        #region IDisposable Members

        public void Dispose()
        {
            // unregister all the registered hot keys.
            for (int i = _currentId; i > 0; i--)
            {
                UnregisterHotKey(_window.Handle, i);
            }

            // dispose the inner native window.
            _window.Dispose();
        }

        #endregion
    }

    /// <summary>
    /// Event Args for the event that is fired after the hot key has been pressed.
    /// </summary>
    public class KeyPressedEventArgs : EventArgs
    {
        private ModifierKeys _modifier;
        private Keys _key;

        internal KeyPressedEventArgs(ModifierKeys modifier, Keys key)
        {
            _modifier = modifier;
            _key = key;
        }

        public ModifierKeys Modifier
        {
            get { return _modifier; }
        }

        public Keys Key
        {
            get { return _key; }
        }
    }

    /// <summary>
    /// The enumeration of possible modifiers.
    /// </summary>
    [Flags]
    public enum ModifierKeys : uint
    {
        Alt = 1,
        Control = 2,
        Shift = 4,
        Win = 8
    }
}

2. Add code to your main class (app startup class)

Check your startup class in Main() method of Program.cs file
Application.Run(new TrayApplicationContext());

public class TrayApplicationContext : ApplicationContext
{
     KeyboardHook hook = new KeyboardHook();

    public TaskTrayApplicationContext()
    {
        // register the event that is fired after the key press.
        hook.KeyPressed += new EventHandler<KeyPressedEventArgs>(Close_App);
    
        // register the control + alt+ F12 combination as hot key.
        hook.RegisterHotKey(ModifierKeys.Control | ModifierKeys.Alt, Keys.F12);
    }

    void Close_App(object sender, KeyPressedEventArgs e)
    {
        Application.Exit();
    }
}

Say thanks to stackoverflow community to make it possible!!