如何使用线程在C＃中的一次发送多个Web请求？ [英] How can you use threading to send multiple web requests at a time in c#?

问题描述

我有一个简单的ASP.NET的小程序，和我想要学习基本的多线程处理，使其运行更加平稳。

I have a simple ASP.NET applet, and I'm trying to learn basic multithreading to make it run more smoothly.

让我们说我有挂在下面的方法的一个按钮：

Let's say I have a button hooked up to the following method:

private NlSearch search;

protected void SearchButtonClick(object sender, EventArgs e)
    {

        int resultCount = search.MakeRequests(SearchForm.Text);
        resultsLabel.Text += SearchForm.Text + ": " + resultCount.ToString() + "     occurances";
    }

所有MakeRequests确实是一个问题，POST请求上做一个第三方网站上搜索和抓取从响应的结果数。然后用结果数沿检索词被添加到页面。

All MakeRequests does is issue a POST request to do a search on a 3rd party website and grabs the number of results from the response. The search term along with the number of results is then added to the page.

但是，如果我是做类似提交新的搜索第一个搜索回应之前，它只会中​​断原来的搜索，只有最近的搜索将它写的结果的标签。

However if I were to do something like submit a new search before the first search has responded, it will simply interrupt the original search and only the most recent search will write it's results to the label.

据我了解有办法用C＃线程要做到这一点，但我无法弄清楚如何正确使用任务做到这一点。我试图把方法的身体变成不带任何参数，我再用于创建和运行任务的第二个方法，但让我觉得我是用不正确的任务，这并没有改变行为。

I understand there's a way to do this with C# threading, but I can't figure out how to use tasks correctly to do this. I tried putting the body of the method into a second method with no arguments that I then used to create and run a task, but this did not change the behavior so I think I was using tasks incorrectly.

任何帮助或建议将AP preciated，谢谢。

Any help or advice would be appreciated, thanks.

编辑：我试过到目前为止：两个答案似乎是工作在检索值，但由于某种原因，没有真正将它们添加到标签的某些原因。例如：

What I've tried so far: both answers seemed to 'work' at retrieving values but for some reason neither actually added them to the label for some reason. For example

protected void NewSearchClick(object sender, EventArgs e)
    {
        new Thread(() => MakeRequest(SearchForm.Text)).Start();
    }

和

protected void MakeRequest(string text)
    {
            int resultCount = search.MakeRequests(text);
            if (resultsLabel != null) resultsLabel.Text += text + ": " + resultCount + "     occurances";
    }

似乎检索值但标签不改变

seemed to retrieve the value but the label does not change.

推荐答案

在一个WPF应用程序，你应该使用两个线程与调度员，因为只有UI线程可以写入标签。更具体地讲，你应该使用调度员作为回调的UI进行任何更新时，任务完成：

In a WPF app, you should use both threads and Dispatcher, because only the UI thread can write to a label. More specifically, you should use the dispatcher as a callback to update anything in the UI when a task is complete:

protected void SearchButtonClick(object sender, EventArgs e)
{
    new Thread(() => MakeRequest(SearchForm.Text)).Start();
}

protected void MakeRequest(string text)
{
    int resultCount = search.MakeRequests(text);

    // tell UI thread to update label
    Dispatcher.BeginInvoke(new Action(() =>
            {
                resultsLabel.Text += text + ": " + resultCount + "     occurances";
            }));
}

EDIT1：使用调度不仅仅是线程

EDIT2：同时使用调度和线程

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