DateTime lastClick = DateTime.Now;
  object obj = new object();
  int i = 0;
  private void Button_Click(object sender, RoutedEventArgs e)
  {
   this.IsEnabled = false;  
   var t = (DateTime.Now - lastClick).TotalMilliseconds;
   i++;
   lastClick = DateTime.Now;
   System.Diagnostics.Debug.Print(t + "," + i + ";" + DateTime.Now);
   Thread.Sleep(2000);   
   this.IsEnabled = true;
  }

private void Button_Click(object sender, RoutedEventArgs e)
  {
   this.IsEnabled = false;
   DispatcherHelper.DoEvents();
   var t = (DateTime.Now - lastClick).TotalMilliseconds;
   i++;
   lastClick = DateTime.Now;
   System.Diagnostics.Debug.Print(t + "," + i + ";" + DateTime.Now);
   Thread.Sleep(2000);   
   this.IsEnabled = true;
  }
  public static class DispatcherHelper
  {
   [SecurityPermissionAttribute(SecurityAction.Demand, Flags = SecurityPermissionFlag.UnmanagedCode)]
   public static void DoEvents()
   {
    DispatcherFrame frame = new DispatcherFrame();
    Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background, new DispatcherOperationCallback(ExitFrames), frame);
    try { Dispatcher.PushFrame(frame); }
    catch (InvalidOperationException) { }
   }
   private static object ExitFrames(object frame)
   {
    ((DispatcherFrame)frame).Continue = false;
    return null;
   }
  }