在任务中等待 async/await [英] Waiting for async/await inside a task

问题描述

我的 main() 中有这个构造，它创建了

I have this construct in my main(), which creates

var tasks = new List<Task>();

var t = Task.Factory.StartNew(
    async () =>
    {
        Foo.Fim();
        await Foo.DoBar();
    });

//DoBar not completed
t.Wait();
//Foo.Fim() done, Foo.DoBar should be but isn't

然而，当我 .Wait for t 时，它不会等待对 DoBar() 的调用完成.我如何让它真正等待?

However, when I .Wait for t, it won't wait for the call to DoBar() to complete. How do I get it to actually wait?

推荐答案

不鼓励使用 Task.Factory.StartNew 和 async-await，你应该使用 Task.Run 代替:

It's discouraged to use Task.Factory.StartNew with async-await, you should be using Task.Run instead:

var t = Task.Run(
    async () =>
    {
        Foo.Fim();
        await Foo.DoBar();
    });

Task.Factory.StartNew api 是在 基于任务的异步模式 (TAP) 和 async-await.它将返回 Task 因为您正在使用 lambda 表达式启动一个任务，该表达式恰好是异步的，因此返回一个任务.Unwrap 将提取内部任务，但 Task.Run 会隐式地为您完成.

The Task.Factory.StartNew api was built before the Task-based Asynchronous Pattern (TAP) and async-await. It will return Task<Task> because you are starting a task with a lambda expression which happens to be async and so returns a task. Unwrap will extract the inner task, but Task.Run will implicitly do that for you.

为了更深入的比较，总有一篇相关的 Stephen Toub 文章:Task.Run vs Task.Factory.StartNew

For a deeper comparison, there's always a relevant Stephen Toub article: Task.Run vs Task.Factory.StartNew

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