使用publisher模式控制频繁的UI输出，避免Winform界面假死

http://www.cnblogs.com/Charltsing/p/publisher.html

最近测试task并发任务的效率与线程池的区别，发现了另外一个问题。task建立任务的速度很快，输出到UI的信息过频，导致UI假死。

private void TestMakeTasks(object obj)
    {
        string msg = "";
         
        //循环创建task
        for (int i = 0; i < 3000; i++)
        {
            //主线程（winform）--子线程（Thread）--工作线程（task）
            //不能在循环里面连续访问UI,会造成UI来不及处理，导致假死。                
            Task<string> tt = Task.Factory.StartNew<string>(test, i);
            tt.ContinueWith((t) =>
            {
                if (t.IsFaulted)
                {
                    string msgexcep = (string.Format("I have observed a {0}", t.Exception.InnerException.GetType().Name));
                    Interlocked.Increment(ref responsecount);
                    Interlocked.Decrement(ref threadscount);
                }
            });
            //Thread.Sleep(1);  //避免过快发送UI更新请求，导致假死。
            msg = " 已发送请求数：" + requestcount.ToString() + " 已完成请求数：" + responsecount.ToString();
 
            //输出线程建立信息给UI，过频会导致假死。<br>                PublishStatus(msg);
 
            Interlocked.Increment(ref threadscount);
            Interlocked.Increment(ref requestcount);
            if (_isStop)
            {
                PublishMessage("正在退出...\r\n");
                break;
            }
        }
        PublishMessage("发送完毕，请等待线程运行完毕！\r\n");
        while (responsecount < requestcount)
        {
            Thread.Sleep(300);
            msg = "!已发送请求数：" + requestcount.ToString() + " 已完成请求数：" + responsecount.ToString();
            PublishStatus(msg);
        }
        _isRunning = false;
        PublishMessage("\r\n全部线程运行完毕！\r\n");
    }

　　为了解决这个问题，考虑使用publisher模式控制UI输出

public class Publisher
    {
        public bool isbusy = false;   //标志
        public delegate void PublishEventHander(object sender, PubEventArgs e);
 
        public event PublishEventHander PublishMessage;
        public event PublishEventHander PublishStatus;
 
        //声明一个可重写的OnPublish的保护函数
        protected virtual void OnPublishMessage(PubEventArgs e)
        {
            if (PublishMessage != null)
            {
                //Sender = this，也就是Publisher
                this.PublishMessage(this, e);
            }
        }
        protected virtual void OnPublishStatus(PubEventArgs e)
        {
            if (PublishStatus != null)
            {
                //Sender = this，也就是Publisher
                this.PublishStatus(this, e);
            }
        }
 
        /// <summary>
        /// 触发publish message事件
        /// </summary>
        public void IssueMessage(string message)
        {
            OnPublishMessage(new PubEventArgs(message));
        }
 
        /// <summary>
        /// 触发publish status事件
        /// </summary>
        public void IssueStatus(string message)
        {
            if (!isbusy) OnPublishStatus(new PubEventArgs(message));        }
    }

　　同时，在UI输出部分，使用Invoke来阻止更多的UI操作（不能使用BeginInvoke）。

private void WriteStatus(string msg)
    {
        if (this.lblStatus.InvokeRequired)
        {
            Invoke(cdWriteStatus, msg);
        }
        else
        {
            UpdatelblMethod(msg);
        }
    }