Sichtbarmachen des oberen oder unteren Endes des Textes eines TextBox-Steuerelements

Sichtbarmachen des oberen oder unteren Endes des Textes eines 
TextBox-Steuerelements
<URL:http://dotnet.mvps.org/dotnet/faqs/?id=textboxscroll&lang=de>
----------------------------------------------------------------------------

Scrolling the textbox control to top or bottom

When using a textbox or richtextbox control for displaying logging
information, it is useful to scroll the recently added line into view.
There are two ways to accomplish this (the first solution will also work
with textbox controls and supports scrolling to the top too).

Vertical scrolling only works with multi-line textboxes (the 'MultiLine'
property must be set to 'True'), and horizontal scrolling requires the
'WordWrap' property to be set to 'False':

\\\
Friend Module TextBoxExtensions
    Private Const WM_VSCROLL As Int32 = &H115
    Private Const WH_HSCROLL As Int32 = &H114

    Private Const SB_TOP As Int32 = 6
    Private Const SB_LEFT As Int32 = 6
    Private Const SB_BOTTOM As Int32 = 7
    Private Const SB_RIGHT As Int32 = 7

    Private Declare Auto Function SendMessage Lib "user32.dll" ( _
        ByVal hwnd As IntPtr, _
        ByVal wMsg As Int32, _
        ByVal wParam As IntPtr, _
        ByVal lParam As IntPtr _
    ) As IntPtr

    <Extension()> _
    Public Sub ScrollToTop(ByVal TextBox As TextBoxBase)
        SendMessage( _
            TextBox.Handle, _
            WM_VSCROLL, _
            New IntPtr(SB_TOP), _
            IntPtr.Zero _
        )
    End Sub

    <Extension()> _
    Public Sub ScrollToLeft(ByVal TextBox As TextBoxBase)
        SendMessage( _
            TextBox.Handle, _
            WH_HSCROLL, _
            New IntPtr(SB_LEFT), _
            IntPtr.Zero _
        )
    End Sub

    <Extension()> _
    Public Sub ScrollToBottom(ByVal TextBox As TextBoxBase)
        SendMessage( _
            TextBox.Handle, _
            WM_VSCROLL, _
            New IntPtr(SB_BOTTOM), _
            IntPtr.Zero _
        )
    End Sub

    <Extension()> _
    Public Sub ScrollToRight(ByVal TextBox As TextBoxBase)
        SendMessage( _
            TextBox.Handle, _
            WH_HSCROLL, _
            New IntPtr(SB_RIGHT), _
            IntPtr.Zero _
        )
    End Sub
End Module
///

Usage:

\\\
With Me.TextBox1
    .AppendText("Hello World")
    .ScrollToBottom()
End With
///

- or -

\\\
Dim LastActiveControl As Control = Me.ActiveControl
With Me.RichTextBox1
    .Focus()
    .AppendText("Hello World!")
    .ScrollToCaret()
End With
LastActiveControl.Focus()
///

The second solution has a side-effect:  Setting the focus to the
richtextbox control may raise validation events.