Public Overridable Sub Undo() 

Dim instance As AnnAutomation
 
instance.Undo()

public virtual void Undo()

public:
virtual void Undo(); 

Public Sub AnnAutomation_Undo(ByVal automation As AnnAutomation)
   If automation.Container.Objects.Count > 0 Then
      ' select the first object in the automation
      automation.StartEditing(automation.Container.Objects(0), False)
      MessageBox.Show("Object has been selected.  Next delete it")
      ' delete this object
      automation.Delete()
      MessageBox.Show("Object has been deleted.  Next undo the operation to bring the object back")

      ' undo the delete operation
      automation.Undo()
      MessageBox.Show("Operation has been undone and the object is back.  Next redo the operation to delete the object again")

      ' redo the delete operation
      automation.Redo()
      MessageBox.Show("Operation has been redone and the object is deleted again.")
   Else
      MessageBox.Show("No objects in the container!")
   End If
End Sub

public void AnnAutomation_Undo(AnnAutomation automation)
{
   if(automation.Container.Objects.Count > 0)
   {
      // select the first object in the automation
      automation.StartEditing(automation.Container.Objects[0], false);
      MessageBox.Show("Object has been selected.  Next delete it");
      // delete this object
      automation.Delete();
      MessageBox.Show("Object has been deleted.  Next undo the operation to bring the object back");

      // undo the delete operation
      automation.Undo();
      MessageBox.Show("Operation has been undone and the object is back.  Next redo the operation to delete the object again");

      // redo the delete operation
      automation.Redo();
      MessageBox.Show("Operation has been redone and the object is deleted again.");
   }
   else
      MessageBox.Show("No objects in the container!");
}