using System.Collections;
namespace Templates.Observer {

 public class Subject {
   // Subject instance variables

   private ArrayList observers = new ArrayList();

   public void Attach(Observer o){
     observers.Add(o);
   }

   public void Detach(Observer o){
     observers.Remove(o);
   }

   public void Notify(){
     foreach(Observer o in observers) o.Update();
   }

   public SubjectState GetState(){
     return new SubjectState();
   }
 }

 public class SubjectState {
   // Selected state of the subject
 }
}