Task.ContinueWith 不耽误

Question

为什么操作1和2同时执行？而不是相隔 30 秒？

运行在 ASP.NET 上的 IIS 下

Task t = Task.Factory.StartNew(() =>
     {
        Console.WriteLine("Operation 1");
     }
    ).ContinueWith(async task =>
    {
        log("sleeping during turn on");
        await Task.Delay(25000);
        log("finished awaiting");
        Thread.Sleep(5000);
        log("finished sleeping");
    }
    ).ContinueWith(
        task =>
        {
             Console.WriteLine("Operation 2");
        }
    );

t.Wait();

Answer 1

首先ContinueWithreturnsTask<Task>，然后你需要.Unwrap它：

Task t = Task.Factory.StartNew(() => {
    Console.WriteLine("Operation 1");
})
.ContinueWith(async task => {
    log("sleeping during turn on");
    await Task.Delay(25000);
    log("finished awaiting");
    Thread.Sleep(5000);
    log("finished sleeping");
})
.Unwrap()
.ContinueWith(task => {
     Console.WriteLine("Operation 2");
});
t.Wait();

为了更深入的理解，您可以检查 ContinueWith 的所有实现：在第一个 ContinueWith 中使用，在第二个中使用。

还要检查async task => { ...，你需要明白它returns Task.

最后说明一下（如果不是理解ContinueWith的问题），最好用await:

Task t = Task.Factory.StartNew(async () => {
    Console.WriteLine("Operation 1");

    log("sleeping during turn on");
    await Task.Delay(25000);
    log("finished awaiting");
    Thread.Sleep(5000);
    log("finished sleeping");

     Console.WriteLine("Operation 2");
});
t.Wait();

Answer 2

Why do operations 1 and 2 execute at the same time? and not 30 seconds apart?

就此而言，简短的回答是 ContinueWith does not understand async. Neither does StartNew。您不应该使用 ContinueWith 或 StartNew.

Instead of StartNew, use Task.Run，而不是 ContinueWith，使用 await:

Task t = Task.Run(async () =>
{
  Console.WriteLine("Operation 1");

  log("sleeping during turn on");
  await Task.Delay(25000);
  log("finished awaiting");
  Thread.Sleep(5000);
  log("finished sleeping");

  Console.WriteLine("Operation 2");
});
t.Wait();

Running under IIS on ASP.NET

因为你在 ASP.NET，you shouldn't be using Task.Run, either：

Console.WriteLine("Operation 1");

log("sleeping during turn on");
await Task.Delay(25000);
log("finished awaiting");
Thread.Sleep(5000);
log("finished sleeping");

Console.WriteLine("Operation 2");

Task.ContinueWith 不耽误

Task.ContinueWith not delaying

c#

asynchronous

task

task-parallel-library