# VB 2008 keyboard hooking



## taurian (Jun 28, 2010)

Hi, I have been trying to build an application for which I need to set low-level keyboard hooks. I thing I am trying to accomplish is that when I press the key "a" I want windows to think I have pressed the key "b". But the problem I am facing is that when I press key "a" it produces "ab". I am providing my code below. Any help will be highly appreciated. Also I would like to know how to detect double and triple key presses (e.g. shift + a and ctrl + alt + b).

Option Strict On
Imports System.Runtime.InteropServices
Public Class Form1
    Private Const KEYEVENTF_EXTENDEDKEY As Long = &H1
    Private Const KEYEVENTF_KEYUP As Long = &H2
    Private Declare Sub keybd_event Lib "user32" (ByVal bVk As Byte, _
    ByVal bScan As Byte, ByVal dwFlags As Long, ByVal dwExtraInfo As Long)

    Private Const WH_KEYBOARD_LL As Integer = 13
    Private Const WM_KEYUP As Integer = &H101
    Private Shared _proc As LowLevelKeyboardProc = AddressOf HookCallback
    Private Shared _hookID As IntPtr = IntPtr.Zero

    Public Declare Auto Function SetWindowsHookEx Lib "user32.dll" ( _
    ByVal idHook As Integer, ByVal lpfn As LowLevelKeyboardProc, _
    ByVal hMod As IntPtr, ByVal dwThreadId As UInteger) As IntPtr

    Public Declare Auto Function UnhookWindowsHookEx _
    Lib "user32.dll" (ByVal hhk As IntPtr) As IntPtr

    Public Declare Auto Function CallNextHookEx _
    Lib "user32.dll" (ByVal hhk As IntPtr, ByVal nCode As Integer, _
    ByVal wParam As IntPtr, ByVal lParam As IntPtr) As IntPtr

    Public Declare Auto Function GetModuleHandle Lib "kernel32.dll" ( _
    ByVal lpModuleName As String) As IntPtr


    Private Shared Function SetHook( _
    ByVal proc As LowLevelKeyboardProc) As IntPtr

        Dim curProcess As Process = Process.GetCurrentProcess()
        Dim curModule As ProcessModule = curProcess.MainModule

        Return SetWindowsHookEx(WH_KEYBOARD_LL, proc, _
        GetModuleHandle(curModule.ModuleName), 0)

    End Function

    Public Delegate Function LowLevelKeyboardProc( _
    ByVal nCode As Integer, ByVal wParam As IntPtr, _
    ByVal lParam As IntPtr) As IntPtr

    Public Shared Function HookCallback( _
    ByVal nCode As Integer, _
    ByVal wParam As IntPtr, ByVal lParam As IntPtr) As IntPtr

        If nCode >= 0 And wParam = CType(WM_KEYUP, IntPtr) Then
            Dim vkCode As Keys = CType(Marshal.ReadInt32(lParam), Keys)
            If vkCode = Keys.A Or vkCode = Keys.A Then
                keybd_event(CByte(Keys.B), 0, KEYEVENTF_EXTENDEDKEY, 0)
            End If
        End If

        Return CallNextHookEx(_hookID, nCode, wParam, lParam)
    End Function

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        _hookID = SetHook(_proc)
    End Sub
    Private Sub Form1_FormClosed(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosedEventArgs) Handles Me.FormClosed
        UnhookWindowsHookEx(_hookID)
    End Sub
End Class


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## abhijangda (Jul 1, 2010)

hey can u just upload ur project here, i has VB 2010, i will convert ur VB 2008 project to VB 2010 project. i can help!!


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## dheeraj_kumar (Jul 6, 2010)

Read this:

A Simple C# Global Low Level Keyboard Hook - CodeProject

This helped me a lot 

Convert the code to VB using Convert C# to VB.NET - A free code conversion tool - developer Fusion


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