class TestClient
    {
        private Thread workThread;
        private SynchronizationContext mainThreadSynContext;
        public event EventHandler Connected;

        public TestClient()//构造函数当然是主线程执行的
        {
            mainThreadSynContext = SynchronizationContext.Current;
            workThread = new Thread(new ThreadStart(DoWork));
        }

        private void OnConnected(object state)//由于是主线程的同步对象Post调用，这个是在主线程中执行的
        {
            if (Connected != null)
                Connected(this, EventArgs.Empty);
        }

        private void DoWork()//这个是workThread线程执行的
        {
            //这儿做些事(连接什么的。。。)

            //这而干完了
            if (Connected != null)
                mainThreadSynContext.Post(new SendOrPostCallback(OnConnected), null);
        }
    }