用并发队列(ConcurrentQueue)实现多线程任务中随时异步回调进度通知(.Net4.0)

本文讲述实现抽象出来的异步通知回调进度通知，用在多层组件中，支持一组task的任意进度回调通知。本文中用到几个.NET 4.0的新方法和TPL方法：Tuple，ConcurrentQueue，SemaphoreSlim，Task...说明：如果你是一个简单的Task可能无需这么复杂，用传入Action同步回调即可，但是注意NotifyProgress也就是在任务执行过程中随时同步通知进度，会造成你任务阻塞。如果你是在UI层，用BackgroundWorkder最简单了。(本文原创于http://mainz.cnblogs.com，转载请注明。)

//异步操作，代替Thread, threadPool
Task _ProgressQueueTask = null;
//限制并发访问资源的线程数，SemaphoreSlim开销低于Semaphore50倍
SemaphoreSlim _ProgressCounter = null;
//并发队列ConcurrentQueue，线程安全的队列
//Tuple：元数据结构，可以方便的访问其item
ConcurrentQueue<tuple<progressaction, string,="" int?="">> _ProgressQueue = new ConcurrentQueue<tuple<progressaction, string,="" int?="">>();
Action<progressaction, string,="" int?=""> _OnProgress;
  public Action<progressaction, string,="" int?=""> OnProgress
  {
      get {  return _OnProgress; }
      set
     {
        _OnProgress = value;
        if (_ProgressQueueTask == null)
        {
                _ProgressQueueTask = new Task(() =>
                {
                       while (true)
                        {
                            Tuple<progressaction, string,="" int?=""> item;
                            //查询队列
                            if (_ProgressQueue.TryDequeue(out item))
                            {
                                OnProgress(item.Item1, item.Item2, item.Item3);
                            }
                            else
                            {
                                //线程等待信号，由NotifyProgress入队列并给予信号
                                _ProgressCounter.Wait();
                            }
                        }
                    },
                    TaskCreationOptions.LongRunning);
             _ProgressCounter = new SemaphoreSlim(0, 10);//初始0，最大限制10
                _ProgressQueueTask.Start();
            }
        }
    }
    //在任何Task的执行过程中，或一组task的执行过程中，可以调用此方法来异步回调随时通知进度，而不会阻塞本任务
    public void NotifyProgress(ProgressAction action, string item = null, long? current = null, long? maxCount = null)
    {
        if (OnProgress != null)
        {
            int? percent = null;
            if (current.HasValue && maxCount.HasValue)
            {
                percent = (int)((double)current.Value / (double)maxCount.Value * 100.0);
            }
            _ProgressQueue.Enqueue(Tuple.Create(action, item, percent));
            _ProgressCounter.Release();
        }
        return;
    }
   public enum ProgressAction
   {
            Adding,
            Extracting,
            Extracted,
            Validating,
            Validated,
            Deleting,
            Deleted,
            Restore
   };
    //用法：
    //中间层
    NotifyProgress(ProgressAction.Extracting, "abc");
    //界面层
    OnProgress = (action, file, percent) =>
                {  
                       //...
                 }