Sending keystrokes to an external program

[bergerkiller]

Hello everyone. I know this subject is dealt with numerious of times on the internet, but the .NET count is scarce. I got the following coding structure:

Public Structure KeyEvent
        Private Declare Function MapVirtualKey Lib "User32.dll" Alias "MapVirtualKeyA" (ByVal uCode As UInt32, ByVal uMapType As MAPVK) As UInt32
        Private Enum MAPVK As UInt32
            ''' <summary>uCode is a virtual-key code and is translated into a scan code.
            ''' If it is a virtual-key code that does not distinguish between left- and
            ''' right-hand keys, the left-hand scan code is returned.
            ''' If there is no translation, the function returns 0.
            ''' </summary>
            ''' <remarks></remarks>
            VK_TO_VSC = 0
            ''' <summary>uCode is a scan code and is translated into a virtual-key code that
            ''' does not distinguish between left- and right-hand keys. If there is no
            ''' translation, the function returns 0.
            ''' </summary>
            ''' <remarks></remarks>
            VSC_TO_VK = 1
            ''' <summary>uCode is a virtual-key code and is translated into an unshifted
            ''' character value in the low-order word of the return value. Dead keys (diacritics)
            ''' are indicated by setting the top bit of the return value. If there is no
            ''' translation, the function returns 0.
            ''' </summary>
            ''' <remarks></remarks>
            VK_TO_CHAR = 2
            ''' <summary>Windows NT/2000/XP: uCode is a scan code and is translated into a
            ''' virtual-key code that distinguishes between left- and right-hand keys. If
            ''' there is no translation, the function returns 0.
            ''' </summary>
            ''' <remarks></remarks>
            VSC_TO_VK_EX = 3
        End Enum
 
        Sub New(ByVal Key As Keys, ByVal EventType As KeyEvent)
            Dim Up As Boolean = EventType = KeyEvent.Up
            Dim Alt As Boolean = (Key And Keys.Alt) = Keys.Alt
            Dim F10 As Boolean = (Key And Keys.F10) = Keys.F10
            If Alt Or F10 Then EventType += 4 'offset to sys_
 
            Me.Key = Key
            Me.EventType = EventType
            Me.Flags = EventFlag.None
            If Up Then Me.Flags = EventFlag.PrevWasDown
            If Up And Not Alt And Not F10 Then Me.Flags += EventFlag.Transition
            If Alt And Not Up Then Me.Flags += EventFlag.AltKeyDown
 
            Dim extended As Boolean = False
            If Key = Keys.LControlKey Or Key = Keys.RControlKey Then extended = True
            If Key = Keys.LShiftKey Or Key = Keys.RShiftKey Then extended = True
            If Key = Keys.LMenu Or Key = Keys.RMenu Then extended = True
            If extended Then Me.Flags += EventFlag.ExtendedKey
            Me.RepeatCount = 0
            Me.scancode = 0
        End Sub
        Sub New(ByVal Character As Char)
            Me.Key = Asc(Character)
            Me.EventType = KeyEvent.CharPress
            Me.Flags = EventFlag.None
        End Sub
        Public EventType As KeyEvent
        Public Key As Keys
        Public RepeatCount As UShort
        Public scancode As Byte
        Public Sub SetScanCode(ByVal key As Keys)
            Me.scancode = MapVirtualKey(key, MAPVK.VK_TO_VSC)
        End Sub
        Public Flags As EventFlag
        Public Enum EventFlag As Byte
            None = 0
            ExtendedKey = 1
            AltKeyDown = 32
            PrevWasDown = 64
            Transition = 128
        End Enum
        Public Enum KeyEvent
            Down = &H100
            Up = &H101
            CharPress = &H102
        End Enum
        Public Function Post(ByVal hwnd As IntPtr) As Boolean
            Dim r() As Byte = BitConverter.GetBytes(Me.RepeatCount)
            Dim value(3) As Byte
            value(0) = r(0)
            value(1) = r(1)
            value(2) = scancode
            value(3) = Flags
            Return API.PostMessage(hwnd, EventType, Key, BitConverter.ToInt32(value, 0))
        End Function
    End Structure

It can send keys and chars. It converts all variables used for the "lparam" to a single int32 value. (4 bytes) Call functions:

    Public Function SendKey(ByVal Key As Keys, ByVal EventType As KeyEvent.KeyEvent, Optional ByVal SendCount As Short = 1)
        Dim k As New KeyEvent(Key, EventType)
        k.RepeatCount = SendCount - 1
        Return SendKey(k)
    End Function
    Public Function SendKey(ByVal k As KeyEvent)
        Return k.Post(Me.hwnd)
    End Function
    Public Function SendKeyChar(ByVal character As Char) As Boolean
        Dim k As New KeyEvent(character)
        Return SendKey(k)
    End Function

Examples:

        Dim w As Window = New Window("Form1").Children(0)
        w.SendKey(Keys.Control Or Keys.A, Window.KeyEvent.KeyEvent.Down)
        w.SendKey(Keys.Control Or Keys.A, Window.KeyEvent.KeyEvent.Up)
        w.SendKey(Keys.A, Window.KeyEvent.KeyEvent.Down)
        w.SendKey(Keys.A, Window.KeyEvent.KeyEvent.Up)
        w.SendKeyChar("A")
        w.SendKeyChar("a")

The function + sub resides in my Window class at this point. I only have on question: what is the use of the "scancode" value? I have set it to a few keys but no noticable changes...neither is there any explanation for it.