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@Larry57
Created April 11, 2013 18:08
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A global Keyboard Hook that works in WPF and is also high CPU load proof. Credits: http://blogs.vertigo.com/personal/ralph/Blog/Lists/Posts/Post.aspx?ID=8
public class KeyboardHook
{
#region pinvoke details
private enum HookType : int
{
WH_JOURNALRECORD = 0,
WH_JOURNALPLAYBACK = 1,
WH_KEYBOARD = 2,
WH_GETMESSAGE = 3,
WH_CALLWNDPROC = 4,
WH_CBT = 5,
WH_SYSMSGFILTER = 6,
WH_MOUSE = 7,
WH_HARDWARE = 8,
WH_DEBUG = 9,
WH_SHELL = 10,
WH_FOREGROUNDIDLE = 11,
WH_CALLWNDPROCRET = 12,
WH_KEYBOARD_LL = 13,
WH_MOUSE_LL = 14
}
public struct KBDLLHOOKSTRUCT
{
public UInt32 vkCode;
public UInt32 scanCode;
public UInt32 flags;
public UInt32 time;
public IntPtr extraInfo;
}
[DllImport("user32.dll")]
private static extern IntPtr SetWindowsHookEx(
HookType code, HookProc func, IntPtr instance, int threadID);
[DllImport("user32.dll")]
private static extern int UnhookWindowsHookEx(IntPtr hook);
[DllImport("user32.dll")]
private static extern int CallNextHookEx(
IntPtr hook, int code, IntPtr wParam, ref KBDLLHOOKSTRUCT lParam);
#endregion
HookType _hookType = HookType.WH_KEYBOARD_LL;
IntPtr _hookHandle = IntPtr.Zero;
HookProc _hookFunction = null;
// hook method called by system
private delegate int HookProc(int code, IntPtr wParam, ref KBDLLHOOKSTRUCT lParam);
// events
public delegate void HookEventHandler(object sender, HookEventArgs e);
public event HookEventHandler KeyDown;
public event HookEventHandler KeyUp;
public KeyboardHook()
{
_hookFunction = new HookProc(HookCallback);
Install();
}
~KeyboardHook()
{
Uninstall();
}
// hook function called by system
private int HookCallback(int code, IntPtr wParam, ref KBDLLHOOKSTRUCT lParam)
{
if (code < 0)
return CallNextHookEx(_hookHandle, code, wParam, ref lParam);
// KeyUp event
if ((lParam.flags & 0x80) != 0 && this.KeyUp != null)
this.KeyUp(this, new HookEventArgs(lParam.vkCode));
// KeyDown event
if ((lParam.flags & 0x80) == 0 && this.KeyDown != null)
this.KeyDown(this, new HookEventArgs(lParam.vkCode));
return CallNextHookEx(_hookHandle, code, wParam, ref lParam);
}
private void Install()
{
// make sure not already installed
if (_hookHandle != IntPtr.Zero)
return;
// need instance handle to module to create a system-wide hook
Module[] list = System.Reflection.Assembly.GetExecutingAssembly().GetModules();
System.Diagnostics.Debug.Assert(list != null && list.Length > 0);
// install system-wide hook
_hookHandle = SetWindowsHookEx(_hookType,
_hookFunction, Marshal.GetHINSTANCE(list[0]), 0);
}
private void Uninstall()
{
if (_hookHandle != IntPtr.Zero)
{
// uninstall system-wide hook
UnhookWindowsHookEx(_hookHandle);
_hookHandle = IntPtr.Zero;
}
}
}
// The callback method converts the low-level keyboard data into something more .NET friendly with the HookEventArgs class.
public class HookEventArgs : EventArgs
{
// using Windows.Forms.Keys instead of Input.Key since the Forms.Keys maps
// to the Win32 KBDLLHOOKSTRUCT virtual key member, where Input.Key does not
public Keys Key;
public bool Alt;
public bool Control;
public bool Shift;
public HookEventArgs(UInt32 keyCode)
{
// detect what modifier keys are pressed, using
// Windows.Forms.Control.ModifierKeys instead of Keyboard.Modifiers
// since Keyboard.Modifiers does not correctly get the state of the
// modifier keys when the application does not have focus
this.Key = (Keys)keyCode;
this.Alt = (System.Windows.Forms.Control.ModifierKeys & Keys.Alt) != 0;
this.Control = (System.Windows.Forms.Control.ModifierKeys & Keys.Control) != 0;
this.Shift = (System.Windows.Forms.Control.ModifierKeys & Keys.Shift) != 0;
}
}
// usage: system-wide keyboard hook
private KeyboardHook _hook;
...
// install system-wide keyboard hook
_hook = new KeyboardHook();
_hook.KeyDown += new KeyboardHook.HookEventHandler(OnHookKeyDown);
// keyboard hook handler
void OnHookKeyDown(object sender, HookEventArgs e)
{
...
}
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