Capture a keyboard keypress in the background

Question

I have a application that runs in the background. I have to generate some event whenever a user press F12 at anytime. So what I need that to capture a key-press. In my application, if any time a user press F10 some event will be performed. I don't understand how to do that?

Have anyone any idea how to do that?

N:B: It is a winforms application. It doesn't need to have focus my form. My main window may remain in system tray but still it have to capture the keypress.

Answer 1

What you want is a global hotkey.

1. Import needed libraries at the top of your class:

   // DLL libraries used to manage hotkeys [DllImport("user32.dll")]  public static extern bool RegisterHotKey(IntPtr hWnd, int id, int fsModifiers, int vlc); [DllImport("user32.dll")] public static extern bool UnregisterHotKey(IntPtr hWnd, int id); 

2. Add a field in your class that will be a reference for the hotkey in your code:

   const int MYACTION_HOTKEY_ID = 1; 

3. Register the hotkey (in the constructor of your Windows Form for instance):

   // Modifier keys codes: Alt = 1, Ctrl = 2, Shift = 4, Win = 8 // Compute the addition of each combination of the keys you want to be pressed // ALT+CTRL = 1 + 2 = 3 , CTRL+SHIFT = 2 + 4 = 6... RegisterHotKey(this.Handle, MYACTION_HOTKEY_ID, 6, (int) Keys.F12); 

4. Handle the typed keys by adding the following method in your class:

   protected override void WndProc(ref Message m) {     if (m.Msg == 0x0312 && m.WParam.ToInt32() == MYACTION_HOTKEY_ID) {         // My hotkey has been typed          // Do what you want here         // ...     }     base.WndProc(ref m); } 

Answer 2

In case you have problem running Otiel's solution:

1. You need to include:

    using System.Runtime.InteropServices; //required for dll import 

2. Another doubt for newbies like me: "top of the class" really means top of your class like this (not namespace or constructor):

   public partial class Form1 : Form {     [DllImport("user32.dll")]     public static extern bool RegisterHotKey(IntPtr hWnd, int id, int fsModifers, int vlc);      [DllImport("user32.dll")]     public static extern bool UnregisterHotKey(IntPtr hWnd, int id); } 

3. You don't need to add user32.dll as reference to the project. WinForms always load this dll automatically.