Global hotkeys in windowless .NET app

Question

I\'ve read similar questions around this issue, including Best way to tackle global hotkey processing in C#? and Set global hotkeys using C#. I\'ve also investigated a NuGet pac

Answer 1

You could also use the NativeWindow class. In the example below, I'm also using an ApplicationContext which is a great way to start a "windowless" application:

static class Program
{
    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new MyContext());
    }
}

public class MyContext : ApplicationContext
{

    private MyHotKey hotkeys = null;

    public MyContext()
    {
        hotkeys = new MyHotKey();
        hotkeys.HotkeyPressed += new MyHotKey.HotkeyDelegate(hotkeys_HotkeyPressed);
    }

    private void hotkeys_HotkeyPressed(int ID)
    {
        switch (ID)
        {
            case 1001:
                MessageBox.Show("Alt-1");
                break;

            case 1002:
                MessageBox.Show("Alt-2");
                break;

            case 1003: // Alt-Q
                Application.Exit();
                break;
            default:
                break;
        }
    }

}

public class MyHotKey : NativeWindow
{

    private const int WM_HOTKEY = 0x0312;
    private const int WM_DESTROY = 0x0002;

    [System.Runtime.InteropServices.DllImport("user32.dll")]
    public static extern bool RegisterHotKey(IntPtr hWnd, int id, int fsModifiers, int vlc);
    [System.Runtime.InteropServices.DllImport("user32.dll")]
    public static extern bool UnregisterHotKey(IntPtr hWnd, int id);

    private List<Int32> IDs = new List<int>();

    public delegate void HotkeyDelegate(int ID);
    public event HotkeyDelegate HotkeyPressed;

    public MyHotKey()
    {
        this.CreateHandle(new CreateParams());
        Application.ApplicationExit += new EventHandler(Application_ApplicationExit);

        RegisterCombo(1001, 1, (int)Keys.D1);
        RegisterCombo(1002, 1, (int)Keys.D2);
        RegisterCombo(1003, 1, (int)Keys.Q);
    }

    private void RegisterCombo(Int32 ID, int fsModifiers, int vlc)
    {
        if (RegisterHotKey(this.Handle, ID, fsModifiers, vlc))
        {
            IDs.Add(ID);
        }
    }

    private void Application_ApplicationExit(object sender, EventArgs e)
    {
        this.DestroyHandle();
    }

    protected override void WndProc(ref Message m)
    {
        switch (m.Msg)
        {
            case WM_HOTKEY:
                if (HotkeyPressed != null)
                {
                    HotkeyPressed(m.WParam.ToInt32());
                }
                break;

            case WM_DESTROY: // fires when "Application.Exit();" is called
                foreach (int ID in IDs)
                {
                    UnregisterHotKey(this.Handle, ID);
                }
                break;
        }
        base.WndProc(ref m);
    }

}

Answer 2

Just create global kbhook like this

Answer 3

Using RegisterHotkey() is boilerplate to detect a hotkey press. I won't repeat it here, you can easily google sample code from the function name.

It does however require a window, no workaround for that. It just doesn't have to be a visible window. By far the simplest way to create an invisible window is to use a Form class, like you do in any Winforms application, and set ShowInTaskbar = False, WindowState = Minimized, FormBorderStyle = FixedToolWindow. Call RegisterHotkey() in your OnLoad() method override, you'll need the Handle property. Easy peasy.