Global hotkey in console application

Question

What you can do is Create a hidden window in your Console application which is used to handle the hotkey notification and raise an event.

The code HERE demonstrates the principal. HERE is an article on handling messages in a Console application, using this you should be able to enhance HotKeyManager to run in a Console Application.

The following update to the HotKeyManager creates a background thread which runs the message loop and handles the windows messages.

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

namespace ConsoleHotKey
{
  public static class HotKeyManager
  {
    public static event EventHandler<HotKeyEventArgs> HotKeyPressed;

    public static int RegisterHotKey(Keys key, KeyModifiers modifiers)
    {
      _windowReadyEvent.WaitOne();
      int id = System.Threading.Interlocked.Increment(ref _id);
      _wnd.Invoke(new RegisterHotKeyDelegate(RegisterHotKeyInternal), _hwnd, id, (uint)modifiers, (uint)key);
      return id;
    }

    public static void UnregisterHotKey(int id)
    {
      _wnd.Invoke(new UnRegisterHotKeyDelegate(UnRegisterHotKeyInternal), _hwnd, id);
    }

    delegate void RegisterHotKeyDelegate(IntPtr hwnd, int id, uint modifiers, uint key);
    delegate void UnRegisterHotKeyDelegate(IntPtr hwnd, int id);

    private static void RegisterHotKeyInternal(IntPtr hwnd, int id, uint modifiers, uint key)
    {      
      RegisterHotKey(hwnd, id, modifiers, key);      
    }

    private static void UnRegisterHotKeyInternal(IntPtr hwnd, int id)
    {
      UnregisterHotKey(_hwnd, id);
    }    

    private static void OnHotKeyPressed(HotKeyEventArgs e)
    {
      if (HotKeyManager.HotKeyPressed != null)
      {
        HotKeyManager.HotKeyPressed(null, e);
      }
    }

    private static volatile MessageWindow _wnd;
    private static volatile IntPtr _hwnd;
    private static ManualResetEvent _windowReadyEvent = new ManualResetEvent(false);
    static HotKeyManager()
    {
      Thread messageLoop = new Thread(delegate()
        {
          Application.Run(new MessageWindow());
        });
      messageLoop.Name = "MessageLoopThread";
      messageLoop.IsBackground = true;
      messageLoop.Start();      
    }

    private class MessageWindow : Form
    {
      public MessageWindow()
      {
        _wnd = this;
        _hwnd = this.Handle;
        _windowReadyEvent.Set();
      }

      protected override void WndProc(ref Message m)
      {
        if (m.Msg == WM_HOTKEY)
        {
          HotKeyEventArgs e = new HotKeyEventArgs(m.LParam);
          HotKeyManager.OnHotKeyPressed(e);
        }

        base.WndProc(ref m);
      }

      protected override void SetVisibleCore(bool value)
      {
        // Ensure the window never becomes visible
        base.SetVisibleCore(false);
      }

      private const int WM_HOTKEY = 0x312;
    }

    [DllImport("user32", SetLastError=true)]
    private static extern bool RegisterHotKey(IntPtr hWnd, int id, uint fsModifiers, uint vk);

    [DllImport("user32", SetLastError = true)]
    private static extern bool UnregisterHotKey(IntPtr hWnd, int id);

    private static int _id = 0;
  }


  public class HotKeyEventArgs : EventArgs
  {
    public readonly Keys Key;
    public readonly KeyModifiers Modifiers;

    public HotKeyEventArgs(Keys key, KeyModifiers modifiers)
    {
      this.Key = key;
      this.Modifiers = modifiers;
    }

    public HotKeyEventArgs(IntPtr hotKeyParam)
    {
      uint param = (uint)hotKeyParam.ToInt64();
      Key = (Keys)((param & 0xffff0000) >> 16);
      Modifiers = (KeyModifiers)(param & 0x0000ffff);
    }
  }

  [Flags]
  public enum KeyModifiers
  {
    Alt = 1,
    Control = 2,
    Shift = 4,
    Windows = 8,
    NoRepeat = 0x4000
  }
}

Here is an example of using HotKeyManager from a Console application

using System;
using System.Windows.Forms;

namespace ConsoleHotKey
{
  class Program
  {
    static void Main(string[] args)
    {
      HotKeyManager.RegisterHotKey(Keys.A, KeyModifiers.Alt);
      HotKeyManager.HotKeyPressed += new EventHandler<HotKeyEventArgs>(HotKeyManager_HotKeyPressed);
      Console.ReadLine();      
    }

    static void HotKeyManager_HotKeyPressed(object sender, HotKeyEventArgs e)
    {
      Console.WriteLine("Hit me!");
    }
  }
}

I just wanted to offer an alternative solution.

I was answering a question for someone who was using this script and I figured this might help someone else who has trouble setting up a global key hook.

Edit: Don't forget to add a reference to System.Windows.Forms

You can do this by selecting Project🢂Add Reference and checking System.Windows.Forms

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

namespace ConsoleKeyhook
{
class Hooky
{
    ///////////////////////////////////////////////////////////
    //A bunch of DLL Imports to set a low level keyboard hook
    ///////////////////////////////////////////////////////////
    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr SetWindowsHookEx(int idHook,
        LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool UnhookWindowsHookEx(IntPtr hhk);

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode,
        IntPtr wParam, IntPtr lParam);

    [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr GetModuleHandle(string lpModuleName);

    ////////////////////////////////////////////////////////////////
    //Some constants to make handling our hook code easier to read
    ////////////////////////////////////////////////////////////////
    private const int WH_KEYBOARD_LL = 13;                    //Type of Hook - Low Level Keyboard
    private const int WM_KEYDOWN = 0x0100;                    //Value passed on KeyDown
    private const int WM_KEYUP = 0x0101;                      //Value passed on KeyUp
    private static LowLevelKeyboardProc _proc = HookCallback; //The function called when a key is pressed
    private static IntPtr _hookID = IntPtr.Zero;
    private static bool CONTROL_DOWN = false;                 //Bool to use as a flag for control key

    public static void Main()
    {
        _hookID = SetHook(_proc);  //Set our hook
        Application.Run();         //Start a standard application method loop
    }

    private static IntPtr SetHook(LowLevelKeyboardProc proc)
    {
        using (Process curProcess = Process.GetCurrentProcess())
        using (ProcessModule curModule = curProcess.MainModule)
        {
            return SetWindowsHookEx(WH_KEYBOARD_LL, proc,
                GetModuleHandle(curModule.ModuleName), 0);
        }
    }

    private delegate IntPtr LowLevelKeyboardProc(int nCode, IntPtr wParam, IntPtr lParam);

    private static IntPtr HookCallback(int nCode, IntPtr wParam, IntPtr lParam)
    {
        if (nCode >= 0 && wParam == (IntPtr)WM_KEYDOWN) //A Key was pressed down
        {
            int vkCode = Marshal.ReadInt32(lParam);           //Get the keycode
            string theKey = ((Keys)vkCode).ToString();        //Name of the key
            Console.Write(theKey);                            //Display the name of the key
            if (theKey.Contains("ControlKey"))                //If they pressed control
            {
                CONTROL_DOWN = true;                          //Flag control as down
            }
            else if (CONTROL_DOWN && theKey == "B")           //If they held CTRL and pressed B
            {
                Console.WriteLine("\n***HOTKEY PRESSED***");  //Our hotkey was pressed
            }
            else if (theKey == "Escape")                      //If they press escape
            {
                UnhookWindowsHookEx(_hookID);                 //Release our hook
                Environment.Exit(0);                          //Exit our program
            }
        }
        else if (nCode >= 0 && wParam == (IntPtr)WM_KEYUP) //KeyUP
        {
            int vkCode = Marshal.ReadInt32(lParam);        //Get Keycode
            string theKey = ((Keys)vkCode).ToString();     //Get Key name
            if (theKey.Contains("ControlKey"))             //If they let go of control
            {
                CONTROL_DOWN = false;                      //Unflag control
            }
        }
        return CallNextHookEx(_hookID, nCode, wParam, lParam); //Call the next hook
    }
}
}

I came up with a solution based on Chris' answer that uses WPF instead of WinForms:

public sealed class GlobalHotkeyRegister : IGlobalHotkeyRegister, IDisposable
{
    private const int WmHotkey = 0x0312;

    private Application _app;
    private readonly Dictionary<Hotkey, Action> _hotkeyActions;

    public GlobalHotkeyRegister()
    {
        _hotkeyActions = new Dictionary<Hotkey, Action>();
        var startupTcs = new TaskCompletionSource<object>();

        Task.Run(() =>
        {
            ComponentDispatcher.ThreadPreprocessMessage += OnThreadPreProcessMessage;

            _app = new Application();
            _app.Startup += (s, e) => startupTcs.SetResult(null);
            _app.Run();
        });

        startupTcs.Task.Wait();
    }

    public void Add(Hotkey hotkey, Action action)
    {
        _hotkeyActions.Add(hotkey, action);

        var keyModifier = (int) hotkey.KeyModifier;
        var key = KeyInterop.VirtualKeyFromKey(hotkey.Key);

        _app.Dispatcher.Invoke(() =>
        {
            if (!RegisterHotKey(IntPtr.Zero, hotkey.GetHashCode(), keyModifier, key))
                throw new Win32Exception(Marshal.GetLastWin32Error());
        });       
    }

    public void Remove(Hotkey hotkey)
    {
        _hotkeyActions.Remove(hotkey);

        _app.Dispatcher.Invoke(() =>
        {
            if (!UnregisterHotKey(IntPtr.Zero, hotkey.GetHashCode()))
                throw new Win32Exception(Marshal.GetLastWin32Error());
        });
    }

    private void OnThreadPreProcessMessage(ref MSG msg, ref bool handled)
    {
        if (msg.message != WmHotkey)
            return;

        var key = KeyInterop.KeyFromVirtualKey(((int) msg.lParam >> 16) & 0xFFFF);
        var keyModifier = (KeyModifier) ((int) msg.lParam & 0xFFFF);

        var hotKey = new Hotkey(keyModifier, key);
        _hotkeyActions[hotKey]();
    }

    public void Dispose()
    {
        _app.Dispatcher.InvokeShutdown();
    }

    [DllImport("user32.dll", SetLastError = true)]
    private static extern bool RegisterHotKey(IntPtr hWnd, int id, int fsModifiers, int vlc);

    [DllImport("user32.dll", SetLastError = true)]
    private static extern bool UnregisterHotKey(IntPtr hWnd, int id);
}

public class Hotkey
{
    public Hotkey(KeyModifier keyModifier, Key key)
    {
        KeyModifier = keyModifier;
        Key = key;
    }

    public KeyModifier KeyModifier { get; }
    public Key Key { get; }

    #region ToString(), Equals() and GetHashcode() overrides
}

[Flags]
public enum KeyModifier
{
    None = 0x0000,
    Alt = 0x0001,
    Ctrl = 0x0002,
    Shift = 0x0004,
    Win = 0x0008,
    NoRepeat = 0x4000
}

To use this, you need to add references to PresentationFramework.dll and WindowsBase.dll.

public static void Main()
{
    using (var hotkeyManager = new GlobalHotkeyManager())
    {
        var hotkey = new Hotkey(KeyModifier.Ctrl | KeyModifier.Alt, Key.S);
        hotkeyManager.Add(hotkey, () => System.Console.WriteLine(hotkey));

        System.Console.ReadKey();
    }
}