using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Text;
public class KeyboardHook : IDisposable
{
public enum Parameters
{
None ,
AllowAltTab ,
AllowWindowsKey ,
AllowAltTabAndWindows ,
PassAllKeysToNextApp
}
//Internal parameters
private bool PassAllKeysToNextApp = false;
private bool AllowAltTab = false;
private bool AllowWindowsKey = false;
//Keyboard API constants
private const int WH_KEYBOARD_LL = 13;
private const int WM_KEYUP = 0x0101;
private const int WM_SYSKEYUP = 0x0105;
//Modifier key constants
private const int VK_SHIFT = 0x10;
private const int VK_CONTROL = 0x11;
private const int VK_MENU = 0x12;
private const int VK_CAPITAL = 0x14;
//Variables used in the call to SetWindowsHookEx
private HookHandlerDelegate proc;
private IntPtr hookID = IntPtr.Zero;
internal delegate IntPtr HookHandlerDelegate (
int nCode , IntPtr wParam , ref KBDLLHOOKSTRUCT lParam );
public event KeyboardHookEventHandler KeyIntercepted;
// Structure returned by the hook whenever a key is pressed
internal struct KBDLLHOOKSTRUCT
{
public int vkCode;
int scanCode;
public int flags;
int time;
int dwExtraInfo;
}
#region Constructors
public KeyboardHook ( )
{
proc = new HookHandlerDelegate ( HookCallback );
using ( Process curProcess = Process.GetCurrentProcess ( ) )
using ( ProcessModule curModule = curProcess.MainModule )
{
hookID = NativeMethods.SetWindowsHookEx ( WH_KEYBOARD_LL , proc ,
NativeMethods.GetModuleHandle ( curModule.ModuleName ) , 0 );
}
}
public KeyboardHook ( string param )
: this ( )
{
if ( !String.IsNullOrEmpty ( param ) && Enum.IsDefined ( typeof ( Parameters ) , param ) )
{
SetParameters ( ( Parameters ) Enum.Parse ( typeof ( Parameters ) , param ) );
}
}
public KeyboardHook ( Parameters param )
: this ( )
{
SetParameters ( param );
}
private void SetParameters ( Parameters param )
{
switch ( param )
{
case Parameters.None:
break;
case Parameters.AllowAltTab:
AllowAltTab = true;
break;
case Parameters.AllowWindowsKey:
AllowWindowsKey = true;
break;
case Parameters.AllowAltTabAndWindows:
AllowAltTab = true;
AllowWindowsKey = true;
break;
case Parameters.PassAllKeysToNextApp:
PassAllKeysToNextApp = true;
break;
}
}
#endregion
#region Check Modifier keys
private void CheckModifiers ( )
{
StringBuilder sb = new StringBuilder ( );
if ( ( NativeMethods.GetKeyState ( VK_CAPITAL ) & 0x0001 ) != 0 )
{
//CAPSLOCK is ON
sb.AppendLine ( "Capslock is enabled." );
}
if ( ( NativeMethods.GetKeyState ( VK_SHIFT ) & 0x8000 ) != 0 )
{
//SHIFT is pressed
sb.AppendLine ( "Shift is pressed." );
}
if ( ( NativeMethods.GetKeyState ( VK_CONTROL ) & 0x8000 ) != 0 )
{
//CONTROL is pressed
sb.AppendLine ( "Control is pressed." );
}
if ( ( NativeMethods.GetKeyState ( VK_MENU ) & 0x8000 ) != 0 )
{
//ALT is pressed
sb.AppendLine ( "Alt is pressed." );
}
Console.WriteLine ( sb.ToString ( ) );
}
#endregion Check Modifier keys
#region Hook Callback Method
private IntPtr HookCallback (
int nCode , IntPtr wParam , ref KBDLLHOOKSTRUCT lParam )
{
bool AllowKey = PassAllKeysToNextApp;
//Filter wParam for KeyUp events only
if ( nCode >= 0 )
{
if ( wParam == ( IntPtr ) WM_KEYUP || wParam == ( IntPtr ) WM_SYSKEYUP )
{
if ( !( lParam.vkCode >= 160 && lParam.vkCode <= 164 ) )
{
CheckModifiers ( );
}
if ( AllowWindowsKey )
{
switch ( lParam.flags )
{
//Ctrl+Esc
case 0:
if ( lParam.vkCode == 27 )
AllowKey = true;
break;
//Windows keys
case 1:
if ( ( lParam.vkCode == 91 ) || ( lParam.vkCode == 92 ) )
AllowKey = true;
break;
}
}
// Alt+Tab
if ( AllowAltTab )
{
if ( ( lParam.flags == 32 ) && ( lParam.vkCode == 9 ) )
AllowKey = true;
}
OnKeyIntercepted ( new KeyboardHookEventArgs ( lParam.vkCode , AllowKey ) );
}
//If this key is being suppressed, return a dummy value
if ( AllowKey == false )
return ( System.IntPtr ) 1;
}
//Pass key to next application
return NativeMethods.CallNextHookEx ( hookID , nCode , wParam , ref lParam );
}
#endregion
#region Event Handling
public void OnKeyIntercepted ( KeyboardHookEventArgs e )
{
if ( KeyIntercepted != null )
KeyIntercepted ( e );
}
public delegate void KeyboardHookEventHandler ( KeyboardHookEventArgs e );
public class KeyboardHookEventArgs : System.EventArgs
{
private string keyName;
private int keyCode;
private bool passThrough;
public string KeyName
{
get { return keyName; }
}
public int KeyCode
{
get { return keyCode; }
}
public bool PassThrough
{
get { return passThrough; }
}
public KeyboardHookEventArgs ( int evtKeyCode , bool evtPassThrough )
{
keyName = ( evtKeyCode ).ToString ( );
keyCode = evtKeyCode;
passThrough = evtPassThrough;
}
}
#endregion
#region IDisposable Members
public void Dispose ( )
{
NativeMethods.UnhookWindowsHookEx ( hookID );
}
#endregion
#region Native methods
[ComVisibleAttribute ( false ) ,
System.Security.SuppressUnmanagedCodeSecurity ( )]
internal class NativeMethods
{
[DllImport ( "kernel32.dll" , CharSet = CharSet.Auto , SetLastError = true )]
public static extern IntPtr GetModuleHandle ( string lpModuleName );
[DllImport ( "user32.dll" , CharSet = CharSet.Auto , SetLastError = true )]
public static extern IntPtr SetWindowsHookEx ( int idHook ,
HookHandlerDelegate lpfn , IntPtr hMod , uint dwThreadId );
[DllImport ( "user32.dll" , CharSet = CharSet.Auto , SetLastError = true )]
[return: MarshalAs ( UnmanagedType.Bool )]
public static extern bool UnhookWindowsHookEx ( IntPtr hhk );
[DllImport ( "user32.dll" , CharSet = CharSet.Auto , SetLastError = true )]
public static extern IntPtr CallNextHookEx ( IntPtr hhk , int nCode ,
IntPtr wParam , ref KBDLLHOOKSTRUCT lParam );
[DllImport ( "user32.dll" , CharSet = CharSet.Auto , ExactSpelling = true , CallingConvention = CallingConvention.Winapi )]
public static extern short GetKeyState ( int keyCode );
}
#endregion
}
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