Invalidate Method

using Leadtools.Annotations.Automation; 
 
using Leadtools.Annotations.Engine; 
using Leadtools.Codecs; 
using Leadtools.Controls; 
using Leadtools.Annotations.Rendering; 
using Leadtools.Annotations.WinForms; 
 
public void AnnAutomation_BeginUndo() 
{ 
   // first create a new undo node 
   _automation.BeginUndo(); 
 
   try 
   { 
      // add a new rectangle object 
      AnnRectangleObject rectObj = new AnnRectangleObject(); 
      rectObj.Rect = LeadRectD.Create(100, 100, 800, 800); 
      rectObj.Stroke = AnnStroke.Create(AnnSolidColorBrush.Create("Blue"), LeadLengthD.Create(1)); 
      rectObj.Fill = AnnSolidColorBrush.Create("Yellow"); 
      _automation.Container.Children.Add(rectObj); 
 
      // Invalidate it 
      _automation.Invalidate(LeadRectD.Empty); 
 
      // Select this object 
      _automation.SelectObject(rectObj); 
 
      // commit the undo node 
      _automation.EndUndo(); 
   } 
   catch (Exception ex) 
   { 
      // in case of errors, cancel the undo node 
      _automation.CancelUndo(); 
      Debug.WriteLine(ex.Message); 
      return; 
   } 
 
   Debug.WriteLine("Object has been added as is now selected. Next will call //Undo// to undo the operation"); 
   _automation.Undo(); 
   Debug.WriteLine("Operation has been undone. Next will call //Redo// to redo the operation"); 
   _automation.Redo(); 
   Debug.WriteLine("Object should be back and selected"); 
}