public V[] GetExtensions()
        {
            Lock readLock = this.readLock;

            readLock.Lock();
            try
            {
                int size = set.Count;
                if (size == 0)
                {
                    return(EmptyList.EmptyArray <V>());
                }
                V[] array = (V[])Array.CreateInstance(type, size);
                set.CopyTo(array, 0);
                return(array);
            }
            finally
            {
                readLock.Unlock();
            }
        }