static readonly T[]  _emptyArray = new T[0];        
            
        // Constructs a List. The list is initially empty and has a capacity
        // of zero. Upon adding the first element to the list the capacity is
        // increased to 16, and then increased in multiples of two as required.
        public List() {
            _items = _emptyArray;
        }

        public T[] ToArray() {
            Contract.Ensures(Contract.Result<T[]>() != null);
            Contract.Ensures(Contract.Result<T[]>().Length == Count);
 
            T[] array = new T[_size];
            Array.Copy(_items, 0, array, 0, _size);
            return array;
        }

        public int Count {
            get {
                Contract.Ensures(Contract.Result<int>() >= 0);
                return _size; 
            }
        }