如何在不等待的情况下安全地调用 C# 中的异步方法 [英] How to safely call an async method in C# without await

问题描述

我有一个 async 方法，它不返回任何数据:

I have an async method which returns no data:

public async Task MyAsyncMethod()
{
    // do some stuff async, don't return any data
}

我从另一个返回一些数据的方法调用它:

I'm calling this from another method which returns some data:

public string GetStringData()
{
    MyAsyncMethod(); // this generates a warning and swallows exceptions
    return "hello world";
}

在不等待的情况下调用 MyAsyncMethod() 会导致因为不等待这个调用，所以当前方法在调用完成之前继续运行"视觉工作室中的警告.在该警告的页面上，它指出:

Calling MyAsyncMethod() without awaiting it causes a "Because this call is not awaited, the current method continues to run before the call is completed" warning in visual studio. On the page for that warning it states:

仅当您确定不想等待异步调用完成并且被调用的方法不会引发任何异常时，才应考虑取消警告..>

You should consider suppressing the warning only if you're sure that you don't want to wait for the asynchronous call to complete and that the called method won't raise any exceptions.

我确定我不想等待调用完成；我不需要也没有时间.但是调用可能引发异常.

I'm sure I don't want to wait for the call to complete; I don't need to or have the time to. But the call might raise exceptions.

我曾多次遇到这个问题，我确信这是一个必须有通用解决方案的常见问题.

I've stumbled into this problem a few times and I'm sure it's a common problem which must have a common solution.

如何在不等待结果的情况下安全地调用异步方法?

对于那些建议我只是等待结果的人，这是响应我们 Web 服务 (ASP.NET Web API) 上的 Web 请求的代码.在 UI 上下文中等待使 UI 线程保持空闲，但在 Web 请求调用中等待将等待 Task 完成后再响应请求，从而无缘无故地增加响应时间.

For people suggesting that I just await the result, this is code that is responding to a web request on our web service (ASP.NET Web API). Awaiting in a UI context keeps the UI thread free, but awaiting in a web request call will wait for the Task to finish before responding to the request, thereby increasing response times with no reason.

推荐答案

如果你想异步"获取异常，你可以这样做:

If you want to get the exception "asynchronously", you could do:

  MyAsyncMethod().
    ContinueWith(t => Console.WriteLine(t.Exception),
        TaskContinuationOptions.OnlyOnFaulted);

这将允许您处理main"线程以外的线程上的异常.线.这意味着您不必等待"从调用 MyAsyncMethod 的线程调用 MyAsyncMethod() ；但是，仍然允许您在异常情况下执行某些操作——但前提是发生异常时.

This will allow you to deal with an exception on a thread other than the "main" thread. This means you don't have to "wait" for the call to MyAsyncMethod() from the thread that calls MyAsyncMethod; but, still allows you to do something with an exception--but only if an exception occurs.

从技术上讲，你可以用 await 做类似的事情:

technically, you could do something similar with await:

try
{
    await MyAsyncMethod().ConfigureAwait(false);
}
catch (Exception ex)
{
    Trace.WriteLine(ex);
}

...如果您需要专门使用 try/catch(或 using)，这将很有用，但我发现 ContinueWith 更明确一点，因为您必须知道 ConfigureAwait(false) 表示.

...which would be useful if you needed to specifically use try/catch (or using) but I find the ContinueWith to be a little more explicit because you have to know what ConfigureAwait(false) means.

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