Task.WhenAll在后台线程中并行运行Task吗? [英] Does Task.WhenAll run Tasks in background thread parallel

问题描述

以下两个代码片段是否相同?

Are the following 2 code fragments do the same?

//--------------------------------------------------
1.
//--------------------------------------------------

var producer = Task.Run(async () =>
{
    await bar.ReadDataAsync();
});

var consumer = Task.Run(async () =>
{
    await bar.WriteDataAsync();
});


await Task.WhenAll(consumer, producer);

//--------------------------------------------------
2.
//--------------------------------------------------

await Task.WhenAll(bar.ReadDataAsync(), bar.WriteDataAsync());

推荐答案

Task.WhenAll不运行任务.此方法不会启动任何任务.

Task.WhenAll does not run the tasks. No tasks are started by this method.

Task.WhenAll 要做的是返回一个新的Task，该Task仅在所有原始任务均已完成时完成.

What Task.WhenAll does do is return a new Task that only completes when all the original tasks have completed.

来自msdn

Task.WhenAll方法

.NET Framework 4.6和4.5

创建一个任务，当所有提供的任务都完成时，该任务将完成 完成.

Creates a task that will complete when all of the supplied tasks have completed.

https://msdn.microsoft.com/zh-CN/library/system.threading.tasks.task.whenall%28v=vs.110%29.aspx

在您的示例中，您呼叫了Task.Run.这是您希望异步运行工作单元的请求.但是，不能保证线程亲和性.这两个工作单元可以同步运行-由默认的TaskScheduler决定.

In your example, you have called Task.Run. This is a request that you would like to run a unit of work asynchronously. However, the thread affinity is not guaranteed. Both units of work may run synchronously - that is up to the default TaskScheduler to decide.

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