Click here to Skip to main content
12,882,806 members (37,923 online)
Click here to Skip to main content
Articles » Languages » C# » General » Downloads

Stats

531.2K views
46.4K downloads
150 bookmarked
Posted 30 May 2007

A Simple C# Global Low Level Keyboard Hook

, 30 May 2007 CPOL
A simple description and sample of creating a global low level keyboard hook in C#
key preview
key preview
bin
Release
key preview sample.zip
key preview.exe
key preview.pdb
key preview.vshost.exe
Properties
key preview.suo
key preview.exe
using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace Utilities {
	/// <summary>
	/// A class that manages a global low level keyboard hook
	/// </summary>
	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
	}
}

By viewing downloads associated with this article you agree to the Terms of Service and the article's licence.

If a file you wish to view isn't highlighted, and is a text file (not binary), please let us know and we'll add colourisation support for it.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Share

About the Author

StormySpike
Software Developer
United States United States
I currently work as a Software Engineer for a company in North Carolina, mainly working with C#.

You may also be interested in...

Permalink | Advertise | Privacy | Terms of Use | Mobile
Web02 | 2.8.170422.1 | Last Updated 30 May 2007
Article Copyright 2007 by StormySpike
Everything else Copyright © CodeProject, 1999-2017
Layout: fixed | fluid