异步/等待中的System.Threading.Timer卡在重复中 [英] System.Threading.Timer with async/await stuck in repeat

问题描述

我想安排每分钟执行一次的功能.此方法调用一个异步函数，它是一个HttpWebRequest.我正在使用异步/等待策略:

I want to schedule a function to be executed every minute. This method calls an asynchronous function which is a HttpWebRequest. I am using the async/await strategy:

var timer = new System.Threading.Timer(async (e) =>
{
    RSSClient rss = new RSSClient(listBoxRSS);
    RSSNotification n = await rss.fetch();
    // ...
    Console.WriteLine("Tick");
}, null, 0, 5000);

控制台将打印滴答"，但仅打印一次.看来计时器因某种原因被卡住了.

The console prints "Tick", but only once. It seems that the timer is stuck for some reason.

在删除异步/等待代码后，计时器仍然可以正常工作:

After removing the async/await code the timer works fine though:

var timer = new System.Threading.Timer((e) =>
{
    Console.WriteLine("Tick");
}, null, 0, 5000);

为什么不重复，如何使用System.Threading.Timer实现异步/等待策略?

Why does it not repeat and how can I implement the async/await strategy using a System.Threading.Timer?

推荐答案

正如达林·迪米特洛夫(Darin Dimitrov)所指出的，由于某种原因，异步方法内部存在一个异常，该异常未在调试器中显示，但可以使用try捕获该异常./赶上.

As pointed out by Darin Dimitrov there was an exception inside of the async method that, for some reason, was not shown in the debugger but could be caught using try/catch.

以下使用async/await的代码可以正常工作:

The following code using async/await works fine:

var timer = new System.Threading.Timer(async (e) =>
{
    await Task.Delay(500);
    Console.WriteLine("Tick");
}, null, 0, 5000);

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