How Can I Set Global Hotkeys in C# to Trigger Events Even When My Application Is Not in Focus?

Set global hotkeys using C# to trigger events (even if the app is not in focus)

This article describes how to set global hotkeys in C# so that events can be triggered even if the application is not in focus.

Question:

Capture keystrokes when the program is not in focus (e.g. Ctrl Alt J) to trigger events within the program.

Solution:

Warning: This code will not trigger events in the console application. Please use WinForms project to implement event functionality.

Custom keyboard hook class:

<code class="language-csharp">public sealed class KeyboardHook : IDisposable
{
    private Window _window = new Window();
    private int _currentId;

    public KeyboardHook()
    {
        // ...
        //  按键事件处理
        // ...
    }

    public void RegisterHotKey(ModifierKeys modifier, Keys key)
    {
        // ...
        // 通过内部原生窗口注册热键
        // ...
    }

    public event EventHandler<KeyPressedEventArgs> KeyPressed;
}</code>

Window class for event handling:

<code class="language-csharp">private class Window : NativeWindow, IDisposable
{
    // ...
    protected override void WndProc(ref Message m)
    {
        // 处理热键按下
        if (m.Msg == WM_HOTKEY)
        {
            // ...
            // 从LParam中提取修饰符和键
            // ...

            // 触发KeyPressed事件
            KeyPressed?.Invoke(this, new KeyPressedEventArgs(modifier, key));
        }
    }

    // ...
}</code>

Usage example:

<code class="language-csharp">public partial class Form1 : Form
{
    private KeyboardHook hook = new KeyboardHook();

    public Form1()
    {
        // ...
        hook.KeyPressed += hook_KeyPressed; //订阅事件
        hook.RegisterHotKey(ModifierKeys.Control | ModifierKeys.Alt, Keys.F12);
        // ...
    }

    void hook_KeyPressed(object sender, KeyPressedEventArgs e)
    {
        // 处理按键事件
    }
}</code>

Note:

• In the usage example, the Control, Alt and F12 key combinations are registered as hotkeys.
• Make sure to convert modifier keys correctly using (ModifierKeys)1, (ModifierKeys)2, etc.

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