Global Keyboard Hook in C#

globalKeyboardHook class

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace WindowsFormsApplication3
{
    class globalKeyboardHook
    {
        #region Constant, Structure and Delegate Definitions
        /// <summary>
        /// defines the callback type for the hook
        /// </summary>
        public delegate int keyboardHookProc(int code, int wParam, ref keyboardHookStruct lParam);

        public struct keyboardHookStruct
        {
            public int vkCode;
            public int scanCode;
            public int flags;
            public int time;
            public int dwExtraInfo;
        }

        const int WH_KEYBOARD_LL = 13;
        const int WM_KEYDOWN = 0x100;
        const int WM_KEYUP = 0x101;
        const int WM_SYSKEYDOWN = 0x104;
        const int WM_SYSKEYUP = 0x105;
        #endregion

        #region Instance Variables
        /// <summary>
        /// The collections of keys to watch for
        /// </summary>
        public List<Keys> HookedKeys = new List<Keys>();
        /// <summary>
        /// Handle to the hook, need this to unhook and call the next hook
        /// </summary>
        IntPtr hhook = IntPtr.Zero;
        #endregion

        #region Events
        /// <summary>
        /// Occurs when one of the hooked keys is pressed
        /// </summary>
        public event KeyEventHandler KeyDown;
        /// <summary>
        /// Occurs when one of the hooked keys is released
        /// </summary>
        public event KeyEventHandler KeyUp;
        #endregion

        #region Constructors and Destructors
        /// <summary>
        /// Initializes a new instance of the <see cref="globalKeyboardHook"/> class and installs the keyboard hook.
        /// </summary>
        public globalKeyboardHook()
        {
            hook();
        }

        /// <summary>
        /// Releases unmanaged resources and performs other cleanup operations before the
        /// <see cref="globalKeyboardHook"/> is reclaimed by garbage collection and uninstalls the keyboard hook.
        /// </summary>
        ~globalKeyboardHook()
        {
            unhook();
        }
        #endregion

        #region Public Methods
        /// <summary>
        /// Installs the global hook
        /// </summary>
        public void hook()
        {
            IntPtr hInstance = LoadLibrary("User32");
            hhook = SetWindowsHookEx(WH_KEYBOARD_LL, hookProc, hInstance, 0);
        }

        /// <summary>
        /// Uninstalls the global hook
        /// </summary>
        public void unhook()
        {
            UnhookWindowsHookEx(hhook);
        }

        /// <summary>
        /// The callback for the keyboard hook
        /// </summary>
        /// <param name="code">The hook code, if it isn't >= 0, the function shouldn't do anyting</param>
        /// <param name="wParam">The event type</param>
        /// <param name="lParam">The keyhook event information</param>
        /// <returns></returns>
        public int hookProc(int code, int wParam, ref keyboardHookStruct lParam)
        {
            if (code >= 0)
            {
                Keys key = (Keys)lParam.vkCode;
                if (HookedKeys.Contains(key))
                {
                    KeyEventArgs kea = new KeyEventArgs(key);
                    if ((wParam == WM_KEYDOWN || wParam == WM_SYSKEYDOWN) && (KeyDown != null))
                    {
                        KeyDown(this, kea);
                    }
                    else if ((wParam == WM_KEYUP || wParam == WM_SYSKEYUP) && (KeyUp != null))
                    {
                        KeyUp(this, kea);
                    }
                    if (kea.Handled)
                        return 1;
                }
            }
            return CallNextHookEx(hhook, code, wParam, ref lParam);
        }
        #endregion

        #region DLL imports
        /// <summary>
        /// Sets the windows hook, do the desired event, one of hInstance or threadId must be non-null
        /// </summary>
        /// <param name="idHook">The id of the event you want to hook</param>
        /// <param name="callback">The callback.</param>
        /// <param name="hInstance">The handle you want to attach the event to, can be null</param>
        /// <param name="threadId">The thread you want to attach the event to, can be null</param>
        /// <returns>a handle to the desired hook</returns>
        [DllImport("user32.dll")]
        static extern IntPtr SetWindowsHookEx(int idHook, keyboardHookProc callback, IntPtr hInstance, uint threadId);

        /// <summary>
        /// Unhooks the windows hook.
        /// </summary>
        /// <param name="hInstance">The hook handle that was returned from SetWindowsHookEx</param>
        /// <returns>True if successful, false otherwise</returns>
        [DllImport("user32.dll")]
        static extern bool UnhookWindowsHookEx(IntPtr hInstance);

        /// <summary>
        /// Calls the next hook.
        /// </summary>
        /// <param name="idHook">The hook id</param>
        /// <param name="nCode">The hook code</param>
        /// <param name="wParam">The wparam.</param>
        /// <param name="lParam">The lparam.</param>
        /// <returns></returns>
        [DllImport("user32.dll")]
        static extern int CallNextHookEx(IntPtr idHook, int nCode, int wParam, ref keyboardHookStruct lParam);

        /// <summary>
        /// Loads the library.
        /// </summary>
        /// <param name="lpFileName">Name of the library</param>
        /// <returns>A handle to the library</returns>
        [DllImport("kernel32.dll")]
        static extern IntPtr LoadLibrary(string lpFileName);
        #endregion
    }
}

C# WinApp

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


namespace WindowsFormsApplication3
{
    public partial class Form1 : Form
    {
        globalKeyboardHook gkh = new globalKeyboardHook();
        [DllImport("user32.dll")]
        private static extern IntPtr GetForegroundWindow();

        [DllImport("user32.dll")]
        private static extern int GetWindowText(IntPtr hWnd, StringBuilder text, int count);

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            gkh.HookedKeys.Add(Keys.A);
            gkh.HookedKeys.Add(Keys.B);
            gkh.HookedKeys.Add(Keys.Control);
            gkh.KeyDown += new KeyEventHandler(gkh_KeyDown);
            gkh.KeyUp += new KeyEventHandler(gkh_KeyUp);
        }

        void gkh_KeyUp(object sender, KeyEventArgs e)
        {
            int chars = 256;
            StringBuilder buff = new StringBuilder(chars);
            // Obtain the handle of the active window.
            IntPtr handle = GetForegroundWindow();
            string test = string.Empty; ;
            if (GetWindowText(handle, buff, chars) > 0)
            {
                test = buff.ToString(); 
            }

            lstLog.Items.Add(test + "Up\t" + e.KeyCode.ToString());
        }

        void gkh_KeyDown(object sender, KeyEventArgs e)
        {
            lstLog.Items.Add("Down\t" + e.KeyCode.ToString());
            //e.Handled = true;  //Optional
        }
    }
}

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Global Window Hook- Windows system event on active window changed


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

namespace ActiveWindowChangeEvent
{
    public partial class Form1 : Form
    {
        delegate void WinEventDelegate(IntPtr hWinEventHook, uint eventType, IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime);
        WinEventDelegate dele = null;
        [DllImport("user32.dll")]
        static extern IntPtr SetWinEventHook(uint eventMin, uint eventMax, IntPtr hmodWinEventProc, WinEventDelegate lpfnWinEventProc, uint idProcess, uint idThread, uint dwFlags);
        private const uint WINEVENT_OUTOFCONTEXT = 0;
        private const uint EVENT_SYSTEM_FOREGROUND = 3;

        [DllImport("user32.dll")]
        static extern IntPtr GetForegroundWindow();

        [DllImport("user32.dll")]
        static extern int GetWindowText(IntPtr hWnd, StringBuilder text, int count);
        private string GetActiveWindowTitle()
        {
            const int nChars = 256;
            IntPtr handle = IntPtr.Zero;
            StringBuilder Buff = new StringBuilder(nChars);
            handle = GetForegroundWindow();

            if (GetWindowText(handle, Buff, nChars) > 0)
            {
                return Buff.ToString();
            }
            return null;
        }

        public void WinEventProc(IntPtr hWinEventHook, uint eventType, IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime)
        {
            Log.Text += GetActiveWindowTitle() + "\r\n";  //Log= RichTextBox
        } 

        public Form1()
        {
            InitializeComponent();
            dele = new WinEventDelegate(WinEventProc);
            IntPtr m_hhook = SetWinEventHook(EVENT_SYSTEM_FOREGROUND, EVENT_SYSTEM_FOREGROUND, IntPtr.Zero, dele, 0, 0, WINEVENT_OUTOFCONTEXT);
        }
    }
}