Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
240 views
in Technique[技术] by (71.8m points)

c# - Return to View with Async Await

I have a process I would like to run in the background. This is executed with a click of an action link.

Action to call:

   public async Task<ActionResult> ProcessRec()
   {
        await Task.Run(() => waitTimer());
        return RedirectToAction("Index", "Home");
   }

   public void waitTimer()
   {
        Thread.Sleep(10000);
   }

This however waits for the full 10 seconds before redirecting me to my "Index, Home" action. I am very new to Await/Async so I know I am interpreting something wrong here. How do I get the application to return to this action, while the waitTimer is executing in the background? Thanks!!

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

await, as you found out, blocks the response from returning to the user before it is done. Normally you would just put your background work on another thread and set it to "fire and forget" by not awaiting, however in ASP.NET IIS will shut down AppDomains that are not being used and Task.Run does not inform IIS that your background thread "is using the AppDomain" so your background thread could be terminated with a Thread.Abort() during an AppDomain shutdown.

If you are using .NET 4.5.2 or newer you can tell IIS you have a background worker that you need to be kept alive via QueueBackgroundWorkItem. You would use it like this

   public ActionResult ProcessRec()
   {
        HostingEnvironment.QueueBackgroundWorkItem(waitTimer);
        return RedirectToAction("Index", "Home");
   }

   public void waitTimer(CancellationToken token)
   {
        Thread.Sleep(10000);
   }
   //You also could do
   public async Task waitTimer2(CancellationToken token)
   {
        await Task.Delay(10000);
   }

Now this does not guarantee that IIS will not shut down your app domain but it does let it know you are in the middle of something and asks for more time when it does try to shut it down (You get up to 90 additional seconds after a shutdown is started to complete all queued background items by default).

For more information read this MSDN blog introducing it.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...