等待Task.Run与等待 [英] await Task.Run vs await

问题描述

我已经在网上搜索了很多关于 Task.Run 与等待异步的问题，但是在这种特定的使用场景下，我并不真正了解其中的区别.我相信情况很简单.

I've searched the web and seen a lot of questions regarding Task.Run vs await async, but there is this specific usage scenario where I don't not really understand the difference. Scenario is quite simple i believe.

await Task.Run(() => LongProcess());

vs

await LongProcess());

其中 LongProcess 是一个异步方法，其中包含一些异步调用，例如使用await ExecuteReaderAsync()来调用db.

where LongProcess is a async method with a few asynchronous calls in it like calling db with await ExecuteReaderAsync() for instance.

问题:

在这种情况下，两者之间是否有区别?任何帮助或输入表示赞赏，谢谢！

Is there any difference between the two in this scenario? Any help or input appreciated, thanks!

推荐答案

Task.Run 可以发布要在不同线程处理的操作.那是唯一的区别.

Task.Run may post the operation to be processed at a different thread. That's the only difference.

这可能有用-例如，如果 LongProcess 不是真正的异步，它将使调用者更快地返回.但是对于真正的异步方法而言，使用 Task.Run 毫无意义，这可能会导致不必要的浪费.

This may be of use - for example, if LongProcess isn't truly asynchronous, it will make the caller return faster. But for a truly asynchronous method, there's no point in using Task.Run, and it may result in unnecessary waste.

但是请小心，因为 Task.Run 的行为将根据重载分辨率而变化.在您的示例中，将选择 Func< Task> 重载，这将(正确)等待 LongProcess 完成.但是，如果使用了不返回任务的委托，则 Task.Run 将仅等待执行直到第一个 await (请注意，这是 TaskFactory的方式).StartNew 会始终表现，因此请不要使用它.)

Be careful, though, because the behaviour of Task.Run will change based on overload resolution. In your example, the Func<Task> overload will be chosen, which will (correctly) wait for LongProcess to finish. However, if a non-task-returning delegate was used, Task.Run will only wait for execution up to the first await (note that this is how TaskFactory.StartNew will always behave, so don't use that).

这篇关于等待Task.Run与等待的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！