http://msdn.microsoft.com/zh-cn/library/dd267265(v=vs.110).aspx

static void Main(string[] args)

        {

            // Construct a ConcurrentQueue.

            ConcurrentQueue<int> cq = new ConcurrentQueue<int>();

            // Populate the queue.

            for (int i = 0; i < 10000; i++) cq.Enqueue(i);

            // Peek at the first element.

            int result;

            if (!cq.TryPeek(out result))

            {

                Console.WriteLine("CQ: TryPeek failed when it should have succeeded");

            }

            else if (result != 0)

            {

                Console.WriteLine("CQ: Expected TryPeek result of 0, got {0}", result);

            }

            int outerSum = 0;

            // An action to consume the ConcurrentQueue.

            Action action = () =>

            {

                int localSum = 0;

                int localValue;

                while (cq.TryDequeue(out localValue)) localSum += localValue;

                Interlocked.Add(ref outerSum, localSum);

            };

            // Start 4 concurrent consuming actions.

            Parallel.Invoke(action, action, action, action);

            Console.WriteLine("outerSum = {0}, should be 49995000", outerSum);

        }