Imports System.Runtime.InteropServices
 
<StructLayout(LayoutKind.Sequential)> _
Public Structure RECT
   Public Left As Integer
   Public Top As Integer
   Public Right As Integer
   Public Bottom As Integer
End Structure
 
 
 
Public Class cLockUpdate
 
   <DllImport("user32.dll", CharSet:=CharSet.Auto)> _
   Private Shared Function GetClientRect(ByVal hWnd As System.IntPtr, ByRef _
   lpRECT As RECT) As Integer
   End Function
 
   Declare Auto Function SendMessage Lib "user32.dll" (ByVal hWnd As IntPtr, _
     ByVal msg As Integer, _
   ByVal wParam As IntPtr, ByVal lParam As IntPtr) As IntPtr
 
   Private Shared Function RedrawWindow(ByVal hWnd As IntPtr, ByRef lprcUpdate _
     As RECT, _
      ByVal hrgnUpdate As IntPtr, ByVal flags As Int32) As Int32
   End Function
 
   Private Const RDW_INVALIDATE As Int32 = &H1
   Private Const WM_SETREDRAW As Int32 = &HB
   Private Const RDW_ALLCHILDREN As Int32 = &H80
   Private Const RDW_UPDATENOW As Int32 = &H100
   Private Const RDW_ERASE As Int32 = &H4
 
 
 
   Public Shared Sub LockWindow(ByVal hWnd As IntPtr, ByVal wLock As Boolean)
      Dim ClientRect As New RECT
 
      If wLock = True Then
         SendMessage(hWnd, WM_SETREDRAW, False, 0&)
      Else
         SendMessage(hWnd, WM_SETREDRAW, True, 0&)
         GetClientRect(hWnd, ClientRect)
         RedrawWindow(hWnd, ClientRect, 0&, RDW_ERASE Or _
            RDW_INVALIDATE Or RDW_ALLCHILDREN Or RDW_UPDATENOW)
      End If
   End Sub
End Class

Public Class Form1
 
   Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
     System.EventArgs) Handles Button1.Click
      Dim sw As New Stopwatch
      sw.Start()
 
      cLockUpdate.LockWindow(Me.ListBox1.Handle, True)
      For x As Integer = 0 To 50000
         Me.ListBox1.Items.Add("Eintrag " & x.ToString)
      Next
      cLockUpdate.LockWindow(Me.ListBox1.Handle, False)
 
      sw.Stop()
      MsgBox("msec: " & sw.ElapsedMilliseconds.ToString)
   End Sub
End Class

Gru?
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