VB.NET Keybord Hook and pinvok - vb.net

Question

Hello I have a VB NET program that uses the following class (http://sim0n.wordpress.com/2009/03/28/vbnet-keyboard-hook-class/)to hook the keybord :
Imports System.Runtime.InteropServices
Public Class KeyboardHook
<DllImport("User32.dll", CharSet:=CharSet.Auto, CallingConvention:=CallingConvention.StdCall)> _
Private Overloads Shared Function SetWindowsHookEx(ByVal idHook As Integer, ByVal HookProc As KBDLLHookProc, ByVal hInstance As IntPtr, ByVal wParam As Integer) As Integer
End Function
<DllImport("User32.dll", CharSet:=CharSet.Auto, CallingConvention:=CallingConvention.StdCall)> _
Private Overloads Shared Function CallNextHookEx(ByVal idHook As Integer, ByVal nCode As Integer, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As Integer
End Function
<DllImport("User32.dll", CharSet:=CharSet.Auto, CallingConvention:=CallingConvention.StdCall)> _
Private Overloads Shared Function UnhookWindowsHookEx(ByVal idHook As Integer) As Boolean
End Function
<StructLayout(LayoutKind.Sequential)> _
Private Structure KBDLLHOOKSTRUCT
Public vkCode As UInt32
Public scanCode As UInt32
Public flags As KBDLLHOOKSTRUCTFlags
Public time As UInt32
Public dwExtraInfo As UIntPtr
End Structure
<Flags()> _
Private Enum KBDLLHOOKSTRUCTFlags As UInt32
LLKHF_EXTENDED = &H1
LLKHF_INJECTED = &H10
LLKHF_ALTDOWN = &H20
LLKHF_UP = &H80
End Enum
Public Shared Event KeyDown(ByVal Key As Keys)
Public Shared Event KeyUp(ByVal Key As Keys)
Private Const WH_KEYBOARD_LL As Integer = 13
Private Const HC_ACTION As Integer = 0
Private Const WM_KEYDOWN = &H100
Private Const WM_KEYUP = &H101
Private Const WM_SYSKEYDOWN = &H104
Private Const WM_SYSKEYUP = &H105
Private Delegate Function KBDLLHookProc(ByVal nCode As Integer, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As Integer
Private KBDLLHookProcDelegate As KBDLLHookProc = New KBDLLHookProc(AddressOf KeyboardProc)
Private HHookID As IntPtr = IntPtr.Zero
Private Function KeyboardProc(ByVal nCode As Integer, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As Integer
If (nCode = HC_ACTION) Then
Dim struct As KBDLLHOOKSTRUCT
Select Case wParam
Case WM_KEYDOWN, WM_SYSKEYDOWN
RaiseEvent KeyDown(CType(CType(Marshal.PtrToStructure(lParam, struct.GetType()), KBDLLHOOKSTRUCT).vkCode, Keys))
Case WM_KEYUP, WM_SYSKEYUP
RaiseEvent KeyUp(CType(CType(Marshal.PtrToStructure(lParam, struct.GetType()), KBDLLHOOKSTRUCT).vkCode, Keys))
End Select
End If
Return CallNextHookEx(IntPtr.Zero, nCode, wParam, lParam)
End Function
Public Sub New()
HHookID = SetWindowsHookEx(WH_KEYBOARD_LL, KBDLLHookProcDelegate, System.Runtime.InteropServices.Marshal.GetHINSTANCE(System.Reflection.Assembly.GetExecutingAssembly.GetModules()(0)).ToInt32, 0)
If HHookID = IntPtr.Zero Then
Throw New Exception("Could not set keyboard hook")
End If
End Sub
Protected Overrides Sub Finalize()
If Not HHookID = IntPtr.Zero Then
UnhookWindowsHookEx(HHookID)
End If
MyBase.Finalize()
End Sub
End Class
In my probgram I'm using the class like this :
Private WithEvents kbHook As New KeyboardHook
Private Sub kbHook_KeyDown(ByVal Key As System.Windows.Forms.Keys) Handles kbHook.KeyDown
MessageBox.show(Key.ToString)
End Sub Private
what I'm looking for is capturing all the user inputs and compare them with a list of words if those inputs match a message box will pop-up showing "matching found". Actually every time a keybord key is pressed a messagebox is showing with the key value typed. I heard about low level hook with pinvoke but I don't know what is it and how to use it . Here is a link that describes better what I want (http://www.youtube.com/watch?v=OgoDzkboT0A) Thank you in advance for any helpful info.

Answer 1

I think your best bet is to buffer all the key presses and after every input check if the value is one of your keywords. You'll probably want to reset the buffer when keys such as space, tab, or enter are pressed. You may also want to handle backspace to remove the last character in the buffer. Good luck!
Private Buffer As String
Private Words As String() = New String() {"bank", "rob", "money"}
Private Sub TextBox1_KeyDown(sender As Object, e As KeyEventArgs) Handles TextBox1.KeyDown
If e.KeyCode = Keys.Space Then
Buffer = String.Empty
Else
Buffer &= Convert.ToChar(e.KeyCode)
End If
If Not Array.IndexOf(Words, Buffer.ToLower()) = -1 Then
MessageBox.Show("Match found!")
End If
End Sub