事件触发后如何重设Task.Delay()?

本文介绍了事件触发后如何重设Task.Delay()?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我试图让FileSystemWatcher超过5分钟未收到任何更改后触发一些代码.

I am trying to let some code fire after my FileSystemWatcher hasn't received any changes for more then 5 minutes.

我当前的方法是在更改后调用 await Task.Delay(); ，希望届时用户已完成.显然，这不是不是的方法.

My current approach is to call a await Task.Delay(); after a change, hoping the user is done by then. This obviously is not the way to go.

所以我的问题是:事件触发后如何重置Task.Delay()?

So my question: How to reset a Task.Delay() after a event fired?

推荐答案

您不能重置" Task.Delay ，但是您可以重置计时器，这使其成为解决问题的理想之选这个问题.

You can't "reset" a Task.Delay, but you can reset a timer which makes it an ideal candidate to solve this problem.

这是一个例子:

private System.Threading.Timer timer; public void Start() { timer = new System.Threading.Timer(_ => fireMyCode()); restartTimer(); } private void onFileChanged(object sender, EventArgs e) { restartTimer(); } private void restartTimer() { timer.Change(TimeSpan.FromMinutes(5), TimeSpan.FromMinutes(5)); }

但是您不必使用计时器，您仍然可以将 Task.Delay 与其他任务一起使用:这个想法是等待两个任务，即延迟和等待文件更改(您可以使用 TaskCompletionSource 从事件中创建"任务).如果延迟任务首先完成，请触发您的代码.

But you don't have to use timers, you can still use Task.Delay with an additional task: the idea is to wait on two tasks, the delay and waiting for the files to change (you can use TaskCompletionSource to "create" a task from an event). If the delay task completes first, fire your code.

这是一个例子:

TaskCompletionSource<object> fileChanged = new TaskCompletionSource<object>(); private void onFileChanged(object sender, EventArgs e) { fileChanged.TrySetResult(null); } private async Task endlessLoop() { while (true) { await handleFilesNotChanged(); } } private async Task handleFilesNotChanged() { Task timeout = Task.Delay(TimeSpan.FromMinutes(5)); Task waitForFile = fileChanged.Task; if (await Task.WhenAny(timeout, waitForFile) == timeout) { fireMyCode(); } fileChanged = new TaskCompletionSource<object>(); }