Invalidate Method

using Leadtools;
using Leadtools.Codecs;
using Leadtools.Controls;

//method to listen to transform Change Event
[TestClass]
void TransformExample()
{
   //listen to Transform Change event
   _viewer.TransformChanged += _Viewer_TransformChanged;
}
//event handler method
[TestClass]
void _Viewer_TransformChanged(object sender, EventArgs e)
{
   //  clear imageViewer InteractiveMode canvas from all objects
   _viewer.InteractiveModeCanvas.Children.Clear();


   //Fixed Rectangle 
   LeadRectD rc1 = LeadRectDHelper.Create(20, 20, 50, 50);

   LeadMatrix matrix = new LeadMatrix(_viewer.Transform.M11, _viewer.Transform.M12,
         _viewer.Transform.M21, _viewer.Transform.M22,
         _viewer.Transform.OffsetX, _viewer.Transform.OffsetY);

   //transformed Rectangle Rectangle 
   LeadRectD rc2 = matrix.TransformRect(rc1);


   // add the fixed blue rectangle at 50, 50 (do not use the viewer transform)
   Rectangle rect = new Rectangle
   {
      Width = rc1.Width,
      Height = rc1.Height,
      Fill = new SolidColorBrush(Windows.UI.Color.FromArgb(255, 0, 0, 255)),
   };

   // Draw the red rectangle. This will be at 50, 50 as well, but will scroll and zoom
   // with the viewer
   Rectangle rect2 = new Rectangle
   {
      Width = rc2.Width,
      Height = rc2.Height,
      Fill = new SolidColorBrush(Windows.UI.Color.FromArgb(255, 0, 255, 0)),
   };


   Canvas.SetLeft(rect, rc1.X);
   Canvas.SetTop(rect, rc1.Y);

   Canvas.SetLeft(rect2, rc2.X);
   Canvas.SetTop(rect2, rc2.Y);

   //add the two rectangles to interactive service canvas
   _viewer.InteractiveModeCanvas.Children.Add(rect);
   _viewer.InteractiveModeCanvas.Children.Add(rect2);
}