Hooking the keyboard message queue in compact framework code

hjgode

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4 Jan 2010CPOL

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Hooking the keyboard message queue in CF2

Download KbdHookCS - Keyboard hooking in compact framework

Here is some nice code to use a keyboard hook implemented in C# for compact framework.

You can use this to catch the funny OS assigned keys like F1, F2, F3, F4, F6 and F7 (Softkey 1 and 2, Phone, End, Volume Up, Volume Down); and last but not least catch the Win Key press.

The hooking class:

using System;
using System.Runtime.InteropServices;
/*
In order to use this class in your program, just declare the variable 
and hook up into HookEvent:
HookKeys hook = new HookKeys();
hook.HookEvent += new HookKeys.HookEventHandler(HookEvent);
hook.Start();
*/
public class HookKeys
{
#region delegates
    public delegate int HookProc(int code, IntPtr wParam, IntPtr lParam);
    public delegate void HookEventHandler(HookEventArgs e, KeyBoardInfo keyBoardInfo);
    public HookEventHandler HookEvent;
#endregion
#region fields
    private HookProc hookDeleg;
    private static int hHook = 0;
#endregion
 
    public HookKeys()
    {
    }
    ~HookKeys(){
        if(hHook!=0)
            this.Stop();
    }
    #region public methods
    ///
    /// Starts the hook
    ///
    public void Start()
    {
        if (hHook != 0)
        {
            //Unhook the previous one
            this.Stop();
        }
        hookDeleg = new HookProc(HookProcedure);
        hHook = SetWindowsHookEx(WH_KEYBOARD_LL, hookDeleg, GetModuleHandle(null), 0);
        if (hHook == 0)
        {
            throw new SystemException("Failed acquiring of the hook.");
        }
        AllKeys(true);
    }
    ///
    /// Stops the hook
    ///
    public void Stop()
    {
        UnhookWindowsHookEx(hHook);
        AllKeys(false);
    }
    #endregion
    #region protected and private methods
    protected virtual void OnHookEvent(HookEventArgs hookArgs, KeyBoardInfo keyBoardInfo)
    {
        if (HookEvent != null)
        {
            HookEvent(hookArgs, keyBoardInfo);
        }
    }
 
    private int HookProcedure(int code, IntPtr wParam, IntPtr lParam)
    {
       KBDLLHOOKSTRUCT hookStruct =  
	(KBDLLHOOKSTRUCT)Marshal.PtrToStructure(lParam, typeof(KBDLLHOOKSTRUCT));
       if (code &lt; 0)
            return CallNextHookEx(hookDeleg, code, wParam, lParam);
       // Let clients determine what to do
       HookEventArgs e = new HookEventArgs();
       e.Code = code;
       e.wParam = wParam;
       e.lParam = lParam;
       KeyBoardInfo keyInfo = new KeyBoardInfo();
       keyInfo.vkCode = hookStruct.vkCode;
       keyInfo.scanCode = hookStruct.scanCode;
       OnHookEvent(e, keyInfo);
       // Yield to the next hook in the chain
       return CallNextHookEx(hookDeleg, code, wParam, lParam);
   }
   #endregion
   #region P/Invoke declarations
 
   [DllImport("coredll.dll")]
   private static extern int AllKeys(bool bEnable);
 
   [DllImport("coredll.dll")]
   private static extern int SetWindowsHookEx
	(int type, HookProc hookProc, IntPtr hInstance, int m);
   [DllImport("coredll.dll")]
   private static extern IntPtr GetModuleHandle(string mod);
   [DllImport("coredll.dll")]
   private static extern int CallNextHookEx(
           HookProc hhk,
           int nCode,
           IntPtr wParam,
           IntPtr lParam
           );
   [DllImport("coredll.dll")]
   private static extern int GetCurrentThreadId();
   [DllImport("coredll.dll", SetLastError = true)]
   private static extern int UnhookWindowsHookEx(int idHook);
   private struct KBDLLHOOKSTRUCT
   {
       public int vkCode;
       public int scanCode;
       public int flags;
       public int time;
       public IntPtr dwExtraInfo;
   }
   const int WH_KEYBOARD_LL = 20;
   #endregion
}
#region event arguments
 
    public class HookEventArgs : EventArgs
    {
        public int Code;    // Hook code
        public IntPtr wParam;   // WPARAM argument
        public IntPtr lParam;   // LPARAM argument
    }
    public class KeyBoardInfo
    {
        public int vkCode;
        public int scanCode;
        public int flags;
        public int time;
    }
#endregion