ListBounded

/// <summary>
    /// A List restricted to contain a limited number of items.
    /// When the list is full an item is added the oldest
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class ListBounded<T>
    {
        #region prop
        //private T[] _array;
        // 'internal' for testing purposes only
        internal T[] _array;

        private int _max;

        private int _head;

        // Is true if more items than _max were added to the list.
        private bool _firstRoundDone = false;

        /// <summary>
        /// Number of available items in the list
        /// </summary>
        public int Count
        {
            get
            {
                return _firstRoundDone ? _max : _head + 1;
            }
        }

        /// <summary>
        /// Oldest item added to the list
        /// </summary>
        public T First
        {
            get
            {
                if (_head < 0)
                    throw new IndexOutOfRangeException("The list is empty");

                if (_firstRoundDone)
                    return _array[(_head + 1) % _max];
                else
                    return _array[0];
            }
        }

        /// <summary>
        /// Last item added to the list
        /// </summary>
        public T Last
        {
            get
            {
                if (_head < 0)
                    throw new IndexOutOfRangeException("The list is empty");

                return _array[_head];
            }
        }
        #endregion

        #region init
        public ListBounded(int maxItem)
        {
            _max = maxItem;
            Clear();
        }
        #endregion

        #region core
        public void Clear()
        {
            _array = new T[_max];
            _head = -1;
        }

        public void Add(T item)
        {
            if (_head == _max - 1) _firstRoundDone = true;

            _head = (_head + 1) % _max;
            _array[_head] = item;
        }

        public List<T> ToList()
        {
            var list = new List<T>();

            lock (this)
            {
                int count = this.Count;
                for (int i = 0; i < count; i++)
                {
                    list.Add(_array[(_head + i) % count]);
                }
            }

            return list;
        }
        #endregion
    }