如何才能TPL任务发送中间结果到父线程？ [英] How can a TPL task send intermediate results to the parent thread?

问题描述

我正在与第三方物流，需要有一个长期运行的TPL任务将结果发送到父UI线程不终止。我曾尝试多种方法，并已在Google上搜寻了不少。有谁知道如何做到这一点与TPL？

I am working with TPL and need to have a long running TPL task send results to the parent UI thread without terminating. I have tried several approaches and have been googling quite a bit. Does anyone know how to make this happen with TPL?

推荐答案

您可以传递一个委托具有周期性结果打电话，和<一href="http://msdn.microsoft.com/en-us/library/system.threading.synchronizationcontext.aspx"><$c$c>SynchronizationContext该任务可以用它来调用在正确的线程回调。这基本上是的BackgroundWorker 做它的方式（和方式的C＃5异步功能将知道里打电话） - 它捕捉<一href="http://msdn.microsoft.com/en-us/library/system.threading.synchronizationcontext.current.aspx"><$c$c>SynchronizationContext.Current调用线程上，然后调用<一个href="http://msdn.microsoft.com/en-us/library/system.threading.synchronizationcontext.post.aspx"><$c$c>Post （IIRC）发布消息到正确的上下文中。然后，您只需要包装在一个<一个原始的回调href="http://msdn.microsoft.com/en-us/library/system.threading.sendorpostcallback.aspx"><$c$c>SendOrPostCallback它执行它时，它得到了正确的线程。

You could pass in a delegate to call with periodic results, and a SynchronizationContext which the task could use to invoke the callback on the correct thread. That's basically the way that BackgroundWorker does it (and the way that the async feature of C# 5 will "know" where to call you back) - it captures SynchronizationContext.Current on the calling thread, then calls Post (IIRC) to post a message to the right context. You then just need to wrap the original callback in a SendOrPostCallback which executes it when it's got to the right thread.

编辑：示例程序：

using System;
using System.Windows.Forms;
using System.Threading;
using System.Threading.Tasks;

class Test
{
    static void Main()
    {
        Form form = new Form();
        Label label = new Label();
        form.Controls.Add(label);
        form.Load += delegate { HandleLoaded(label); };
        Application.Run(form);
    }

    static void HandleLoaded(Label label)
    {
        Action<string> callback = text => label.Text = text;
        StartTask(callback);
    }

    static void StartTask(Action<string> callback)
    {
        SendOrPostCallback postCallback = obj => callback((string) obj);
        SynchronizationContext context = SynchronizationContext.Current;

        Task.Factory.StartNew(() => {
            for (int i = 0; i < 100; i++)
            {
                string text = i.ToString();
                context.Post(postCallback, text);
                Thread.Sleep(100);
            }
        });
    }
}

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