线程同步Demo：SynchronizationContext和EventWaitHandle：异步和同步

涉及到两个类：FileUpload和调用方。
1、FileUpload上传是时使用异步方式，但需要向调用方（另一线程）发布状态信息（例子里只有上传完毕状态，实际可以包括进度等状态），
    调用方不想处理多线程问题，于是考虑SynchronizationContext
2、例子里调用方需要等待上传线程完成，于是用了EventWaitHandle，好像是找麻烦了，呵呵

  1using System;
  2using System.Collections.Generic;
  3using System.Linq;
  4using System.Text;
  5using System.Threading;
  6
  7namespace ConsoleApplication1
  8{
  9    /**//// <summary>
 10    /// 不同线程子键同步调用的辅助类
 11    /// </summary>
 12    internal sealed class OrderedSynchronizationContext : SynchronizationContext
 13    {
 14        fields#region fields
 15        private Queue<KeyValuePair<SendOrPostCallback, object>> pendingCallbacks = new Queue<KeyValuePair<SendOrPostCallback, object>>();
 16        #endregion
 17
 18        functions#region functions
 19        public override void Post(SendOrPostCallback d, object state)
 20        {
 21            lock (this.pendingCallbacks)
 22            {
 23                this.pendingCallbacks.Enqueue(new KeyValuePair<SendOrPostCallback, object>(d, state));
 24                if (this.pendingCallbacks.Count == 1)
 25                {
 26                    ThreadPool.QueueUserWorkItem(new WaitCallback(this.ProcessPendingCallbacks));
 27                }
 28            }
 29        }
 30
 31        private void ProcessPendingCallbacks(object state)
 32        {
 33            KeyValuePair<SendOrPostCallback, object> pair = new KeyValuePair<SendOrPostCallback, object>();
 34            bool flag = false;
 35            do
 36            {
 37                lock (this.pendingCallbacks)
 38                {
 39                    if (this.pendingCallbacks.Count <= 0)
 40                    {
 41                        break;
 42                    }
 43                    pair = this.pendingCallbacks.Dequeue();
 44                }
 45                pair.Key(pair.Value);
 46            }
 47            while (flag);
 48        }
 49        #endregion
 50    }
 51
 52    public delegate void UploadCompletedEventHandler();
 53
 54    /**//// <summary>
 55    /// 模拟异步文件上传
 56    /// </summary>
 57    class FileUpload
 58    {
 59        public event UploadCompletedEventHandler Uploaded;
 60        private SynchronizationContext _syncContext;
 61        
 62        EventWaitHandle _waitHandle;
 63        
 64        public FileUpload(EventWaitHandle waitHandle)
 65        {
 66            this._syncContext = SynchronizationContext.Current ?? new OrderedSynchronizationContext();
 67            this._waitHandle = waitHandle;
 68        }
 69
 70        public void Upload()
 71        {
 72            Console.WriteLine("Upload.Begin");
 73            //模拟异步
 74            ThreadStart ts = new ThreadStart(DoUpload);            
 75            new Thread(ts).Start();            
 76        }
 77
 78        void DoUpload()
 79        {
 80            //模拟上传
 81            for (int i = 0; i < 5; i++)
 82            {
 83                Thread.Sleep(400);
 84                Console.WriteLine("uploading {0}", i);
 85            }
 86            Console.WriteLine("DoUpload.Completed");
 87            if (Uploaded != null)
 88            {
 89                //调用外部事件
 90                if (SynchronizationContext.Current == this._syncContext)
 91                {
 92                    Uploaded();
 93                }
 94                else
 95                {                 
 96                    _syncContext.Post(state =>
 97                        {
 98                            Uploaded();
 99                            
100                            if (_waitHandle != null)
101                            {
102                                _waitHandle.Set();
103                            }
104                        }, null);
105                }
106            }
107        }
108    }
109
110    class Program
111    {
112        static void Main(string[] args)
113        {
114            ManualResetEvent asyncEvent = new ManualResetEvent(false);
115            FileUpload upload = new FileUpload(asyncEvent);
116            upload.Uploaded += () =>
117                {
118                    Console.WriteLine("上载事件触发！");
119                };
120            Console.WriteLine("开始调用上载");
121            upload.Upload();
122            Console.WriteLine("异步上载立即返回");
123            
124            asyncEvent.WaitOne();
125            Console.WriteLine("上载完毕！");
126        }        
127    }
128}

结果：

开始调用上载
Upload.Begin...
异步上载立即返回
uploading 0...
uploading 1...
uploading 2...
uploading 3...
uploading 4...
DoUpload.Completed
上载事件触发！
上载完毕！