Queue with capacity limit

limitedQueue.cs

    /// <summary>
    /// Queue with limit (last items are removed when limit is reached)
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class LimitedQueue<T> : ConcurrentQueue<T>
    {

        private object _syncRoot = new object();
        private int? _maxCapacity;

        public LimitedQueue() { _maxCapacity = null; }
        public LimitedQueue(int capacity) { _maxCapacity = capacity; }

        public ICollection<T> All
        {
            get
            {
                lock (_syncRoot)
                {
                    return this.ToList();
                }
            }
        }

        public void Add(T newElement)
        {
            if (Count >= _maxCapacity)
            {
                T o;
                TryDequeue(out o);
            }
            Enqueue(newElement);
        }
    }