How can I register a global hot key to say CTRL+SH

Question

I'm building an application in C# using WPF. How can I bind to some keys?

Also, how can I bind to the Windows key?

Answer 1

RegisterHotKey() suggested by John could work - the only catch is that it requires an HWND (using PresentationSource.FromVisual(), and casting the result to an HwndSource).

However, you'll also need to respond to the WM_HOTKEY message - I'm not sure if there is a way to get access to the WndProc of a WPF window or not (which can be done for Windows Forms windows).

Answer 2

This is similar to the answers already given, but I find it a bit cleaner:

using System;
using System.Windows.Forms;

namespace GlobalHotkeyExampleForm
{
    public partial class ExampleForm : Form
    {
        [System.Runtime.InteropServices.DllImport("user32.dll")]
        private static extern bool RegisterHotKey(IntPtr hWnd, int id, int fsModifiers, int vk);
        [System.Runtime.InteropServices.DllImport("user32.dll")]
        private static extern bool UnregisterHotKey(IntPtr hWnd, int id);

        enum KeyModifier
        {
            None = 0,
            Alt = 1,
            Control = 2,
            Shift = 4,
            WinKey = 8
        }

        public ExampleForm()
        {
            InitializeComponent();

            int id = 0;     // The id of the hotkey. 
            RegisterHotKey(this.Handle, id, (int)KeyModifier.Shift, Keys.A.GetHashCode());       // Register Shift + A as global hotkey. 
        }

        protected override void WndProc(ref Message m)
        {
            base.WndProc(ref m);

            if (m.Msg == 0x0312)
            {
                /* Note that the three lines below are not needed if you only want to register one hotkey.
                 * The below lines are useful in case you want to register multiple keys, which you can use a switch with the id as argument, or if you want to know which key/modifier was pressed for some particular reason. */

                Keys key = (Keys)(((int)m.LParam >> 16) & 0xFFFF);                  // The key of the hotkey that was pressed.
                KeyModifier modifier = (KeyModifier)((int)m.LParam & 0xFFFF);       // The modifier of the hotkey that was pressed.
                int id = m.WParam.ToInt32();                                        // The id of the hotkey that was pressed.


                MessageBox.Show("Hotkey has been pressed!");
                // do something
            }
        }

        private void ExampleForm_FormClosing(object sender, FormClosingEventArgs e)
        {
            UnregisterHotKey(this.Handle, 0);       // Unregister hotkey with id 0 before closing the form. You might want to call this more than once with different id values if you are planning to register more than one hotkey.
        }
    }
}

I've found it on fluxbytes.com.

Answer 3

A co-worker wrote a sample on how to create a low-level keyboard hook to be used with WPF.

http://blogs.vertigo.com/personal/ralph/Blog/Lists/Posts/Post.aspx?ID=8

Answer 4

I'm not sure of what you mean by "global" here, but here it goes (I'm assuming you mean a command at the application level, for example, Save All that can be triggered from anywhere by Ctrl + Shift + S.)

You find the global UIElement of your choice, for example, the top level window which is the parent of all the controls where you need this binding. Due to "bubbling" of WPF events, events at child elements will bubble all the way up to the root of the control tree.

Now, first you need

1. to bind the Key-Combo with a Command using an InputBinding like this
2. you can then hookup the command to your handler (e.g. code that gets called by SaveAll) via a CommandBinding.

For the Windows Key, you use the right Key enumerated member, Key.LWin or Key.RWin

    public WindowMain()
    {
       InitializeComponent();
       // Bind Key
       InputBinding ib = new InputBinding(
           MyAppCommands.SaveAll,
           new KeyGesture(Key.S, ModifierKeys.Shift | ModifierKeys.Control));
       this.InputBindings.Add(ib);
       // Bind handler
       CommandBinding cb = new CommandBinding( MyAppCommands.SaveAll);
       cb.Executed += new ExecutedRoutedEventHandler( HandlerThatSavesEverthing );
       this.CommandBindings.Add (cb );
    }

    private void HandlerThatSavesEverthing (object obSender, ExecutedRoutedEventArgs e)
    {
      // Do the Save All thing here.
    }

Answer 5

Baboon's solution works best because you may have multiple windows. I did tweak it so it uses the PreviewKeyDownEvent instead of the PreviewKeyUpEvent in order to handle repetition in keystrokes.

I would advise against OS-level registration unless you are writing something like a snipping tool or an audio recording app as it will let you access functionality when the window is not focused.