[英]Cancel task and wait for it to finish
I have a time consuming task which I need to run in a separate thread to avoid locking the GUI thread. 我有一个耗时的任务,我需要在一个单独的线程中运行,以避免锁定GUI线程。 As this task progresses, it updates a specific GUI control.
随着此任务的进行,它会更新特定的GUI控件。
The catch is that the user might move to another part of the GUI before the task is over, and in that case, I have to: 问题是用户可能在任务结束之前移动到GUI的另一部分,在这种情况下,我必须:
For a concrete example, imagine the form has two parts: one where you navigate a directory tree, and another where you display thumbnails. 举一个具体的例子,假设表单有两个部分:一个用于导航目录树,另一个用于显示缩略图。 When the user navigates to another directory, thumbnails need to be refreshed.
当用户导航到另一个目录时,需要刷新缩略图。
First I thought of using a BackgroundWorker
and an AutoResetEvent
to wait for cancellation, but I must have messed something because I got deadlocked when cancelling. 首先我想到使用
BackgroundWorker
和AutoResetEvent
等待取消,但我必须弄乱一些东西,因为我在取消时遇到了死锁。 Then I read about TPL, which is supposed to replace BGW and more primitive mechanisms. 然后我读到了关于TPL,它应该取代BGW和更原始的机制。
Can this be done easily using TPL? 使用TPL可以轻松完成吗?
A few things to note: 有几点需要注意:
You can get a CancellationToken
from a CancellationTokenSource
你可以得到
CancellationToken
从CancellationTokenSource
Task cancellation is a cooperative action: if your task does not periodically check the CancellationToken.IsCancellationRequested
property, it doesn't matter how many times you try to cancel the task, it will merrily churn away. 任务取消是一种合作行为:如果您的任务没有定期检查
CancellationToken.IsCancellationRequested
属性,那么尝试取消任务的次数并不重要,它会随意地流失。
Those things said, here's the general idea: 那些事情说,这是一般的想法:
void Main()
{
var tokenSource = new CancellationTokenSource();
var myTask = Task.Factory
.StartNew(() => DoWork(tokenSource.Token), tokenSource.Token);
Thread.Sleep(1000);
// ok, let's cancel it (well, let's "request it be cancelled")
tokenSource.Cancel();
// wait for the task to "finish"
myTask.Wait();
}
public void DoWork(CancellationToken token)
{
while(!token.IsCancellationRequested)
{
// Do useful stuff here
Console.WriteLine("Working!");
Thread.Sleep(100);
}
}
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