如何在计时器中使用异步和等待 [英] how to use async and await in timer

问题描述

我的Windows应用程序的要求是:

My windows app's requirement are:

1. 使用HttpWebRequest每3秒在一个线程中获取一次Web请求/响应.(执行此Web请求/响应的总数大约为10个线程.)

1. Using HttpWebRequest get web request/response every 3 seconds in one thread.(total is about 10 threads for doing this web request/response.)

每个线程使用一些全局变量.

Each thread use some global variables.

我想使用System.Timers.Timer并异步并等待.但是我不知道这是获得高性能的最佳方法.然后如何测试它们.我在C#中是绿色的.

I want to use a System.Timers.Timer and async and await. But I don't know that is a best way for high performance. And then how to test them. I am a green in C#.

推荐答案

您可以编写如下的RepeatActionEvery()方法.

You could write a RepeatActionEvery() method as follows.

它的参数是:

• action-您要经常重复的操作.
• interval-调用action()之间的延迟间隔.
• cancellationToken-用于取消循环的令牌.

• action - The action you want to repeat every so often.
• interval - The delay interval between calling action().
• cancellationToken - A token you use to cancel the loop.

这是一个可编译的控制台应用程序，演示了如何调用它.对于ASP应用程序，您可以在适当的地方调用它.

Here's a compilable console application that demonstrates how you can call it. For an ASP application you would call it from an appropriate place.

请注意，您需要一种取消循环的方法，这就是为什么我将CancellationToken传递给RepeatActionEvery()的原因.在此示例中，我使用了一个取消来源，该来源会在8秒钟后自动取消.您可能必须提供一个取消源，在适当的时候为其提供其他一些称为.Cancel()的代码. 有关详细信息，请参见此处.

Note that you need a way to cancel the loop, which is why I pass a CancellationToken to RepeatActionEvery(). In this sample, I use a cancellation source which automatically cancels after 8 seconds. You would probably have to provide a cancellation source for which some other code called .Cancel() at the appropriate time. See here for more details.

using System;
using System.Threading;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    sealed class Program
    {
        void run()
        {
            CancellationTokenSource cancellation = new CancellationTokenSource(
              TimeSpan.FromSeconds(8));
            Console.WriteLine("Starting action loop.");
            RepeatActionEvery(() => Console.WriteLine("Action"), 
              TimeSpan.FromSeconds(1), cancellation.Token).Wait();
            Console.WriteLine("Finished action loop.");
        }

        public static async Task RepeatActionEvery(Action action, 
          TimeSpan interval, CancellationToken cancellationToken)
        {
            while (true)
            {
                action();
                Task task = Task.Delay(interval, cancellationToken);

                try
                {
                    await task;
                }
                catch (TaskCanceledException)
                {
                    return;
                }
            }
        }

        static void Main(string[] args)
        {
            new Program().run();
        }
    }
}

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