public object GetFront()
 {
     if (IsEmpty())
     {
         throw new EmptyDequeException("The Deque is empty");
     }
     return(front.GetData());
 }
 public object GetBack()
 {
     if (IsEmpty())
     {
         throw new EmptyDequeException("The Deque is empty");
     }
     return(back.GetData());
 }