Preventing Controls from Redrawing

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

Private Const WM_SETREDRAW As Int32 = &HB

⋮

With Me.RichTextBox1
    SendMessage( _
        .Handle, WM_SETREDRAW, New IntPtr(CInt(False)), IntPtr.Zero _
    )

    ' Manipulate contents.
    For i As Integer = 0 To .TextLength
        .SelectionStart = i
        .SelectionLength = 1
        .SelectionColor = Color.Red
        .SelectionFont = New Font(.SelectionFont, FontStyle.Bold)
    Next i
    SendMessage( _
        .Handle, WM_SETREDRAW, New IntPtr(CInt(True)), IntPtr.Zero _
    )
    .Refresh()
End With