configureawait – Task.ConfigureAwait and WhenAll

Dec 22, 2016 · Now, we will analyse why a deadlock occurs in an UI application (and not in most console applications) and why ConfigureAwait(false) solves this issue.. First

When you have server-side code (i.e. some ApiController) and your functions are asynchronous – so they return Task – is it considered best practice that any time you await functions that you call ConfigureAwait(false)?. I had read that it is more performant since it doesn’t have to switch thread contexts back to the original thread context.

Update: ASP.NET Core does not have a SynchronizationContext . If you are on ASP.NET Core, it does not matter whether you use ConfigureAwait(falseベスト アンサー · 583Brief answer to your question: No. You shouldn’t call ConfigureAwait(false) at the application level like that. TL;DR version of the long answer:124The biggest draw back I’ve found with using ConfigureAwait(false) is that the thread culture is reverted to the system default. If you’ve configur20I have some general thoughts about the implementation of Task : Task is disposable yet we are not supposed to use using . ConfigureAwait was i11$(“#change-alert”).hide();
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c# – Why would I bother to use Task.ConfigureAwait
c# – What are the differences between using ConfigureAwait


Dec 11, 2019 · .NET added async/await to the languages and libraries over seven years ago. In that time, it’s caught on like wildfire, not only across the .NET ecosystem, but also being replicated in a myriad of other languages and frameworks. It’s also seen a ton of improvements in .NET,

Configures an awaiter used to await this . Namespace: System.Threading.Tasks Assemblies: System.Threading.Tasks.dll, mscorlib.dll, netstandard.dll, System.Runtime.dll

A Glance at The Past

Feb 09, 2017 · One of the general recommendations you may often read is to use ConfigureAwait(false) in library code. This is so that when the library is used, it does not block the synchronization context in use by the application (e.g. the UI thread). If the library doesn’t know anything about the app, it

May 20, 2017 · 之前MVC利用MvcHtmlString封装通用下拉菜单,菜单数据需要从webapi获取,自然用到了 await Http Client.GetAsync(Url)方法,前端 @Html.SelectCategory调用的时候会发生死锁。

ライブラリの中で非同期メソッドを呼ぶときは、ConfigureAwait(false) を使用してデッドロックを回避する、と多くのサイトで書かれています。 次のように待つ必要がない場合に関しても、ConfigureAwait(false) を使用するべきなのでしょうか? もちろん処理の内容によるとは思うのですが、

※個人的な備忘録的なものです。 こっちとかこっちのが良くまとめられています。 ライブラリ制作者向けの内容になっているのでアプリ製作者にはあまり関係がないかもしれません なお、サンプルコードは全てWindowsストアアプリとして実行したものとします デッドロックで泣きを見ないよう

デフォルトではConfigureAwaitはtrueになっているのですが trueの場合awaitで非同期処理を同期させた後の処理をUIスレッドにコンテキストスイッチします。

Sep 21, 2014 · To ConfigureAwait or not to ConfigureAwait? Sep 21, 2014 • Eli Arbel. When awaiting tasks in C#, you have the option to configure how the continuation behaves – whether it uses the Synchronization Context or not.. This can be pretty important, especially when awaiting tasks in code that was initialized from a UI thread, which has a Synchronization Context.

New Keywords

I have been using the Task-based asynchronous programming model introduced in C# 5 (.NET 4.5) for a while now and it truly changed my life (at least as far as writing async code is concerned!). No more callbacks and non-linear flow. The code we write with the async/await paradigm is very similar to what we would write in a synchronously fashion which makes it far easier to follow and understand.

The default awaiter attempts to restore the await’s continuation to the original captured context, which can cause a deadlock.In most cases (except for the UI), you do not need to restore the context, so the awaiter should always be configured explicitly.

Remote Web API

What ConfigureAwait(false) does is create an awaitable that does not run the continuation of the awaited task on the previous synchronization context. Queuing the continuation on the synchronization context is much slower than just running it in parallel on any available thread, in addition to the potential deadlocks.. So, arguably you always want the effect of ConfigureAwait(false), unless

Feb 19, 2018 · Thanks for the clarification @JulienBara.. I got to understand this a bit better recently. As I understand now, the ConfigureAwait(false) is recommended for libraries, so that when the awaited task completes, the result is not delivered in the same thread (synchronized) that created the task, because that’s costly and it’s only needed for UI and ASP.NET (not Core) and hence it should not be a

Jan 11, 2019 · 昨天在做项目的时候,用的dapper查数据用的QueryAsync 异步方法。给上级做代码审核时,上级说最好加上ConfigureAwait(false).能减少一些性能开销。 因为之前没用过所以看了 clr via c# 26 27章,以及参考网上资料。

Cause. An asynchronous method awaits a Task directly.. Rule description. When an asynchronous method awaits a Task directly, continuation occurs in the same thread that created the task. This behavior can be costly in terms of performance and can result in a deadlock on the UI thread.

Apr 11, 2017 · The reason ConfigureAwait is used here is to enable tasks to continue on any available thread. For more information on why this is important, check out the article Context Matters.Suffice it to say, for library code that doesn’t care which thread it executes on, you should use ConfigureAwait(false) every time you use await.Eventually, you will find that adding ConfigureAwait all over the place


May 20, 2017 · Coworker and I investigated a cool issue with deadlocks we found some time ago when porting some async code from one service to another. The difference was that one was written with async/await down to the controller, and the other follows legacy Task.Run model.

UI Example

Apr 24, 2019 · And one of these is the usage of ConfigureAwait call. Let’s take this simple class. class AwaitUsingConfigureAwaitTest: IAsyncDisposable { public async ValueTask DisposeAsync() { await Task.CompletedTask; } public void Dummy() { } } The DisposeAsync is just dummy, you don’t have to think about it here.

The Task Parallel Library in conjunction with the async and await keywords are great but there are some subtleties which you should consider. One of these is the use of the ConfigureAwait method.

Стратегия, когда библиотечный код полностью покрывается ConfigureAwait(false), изменяет поведение по умолчанию, и, что более важно, такой подход лишает разработчиков “клиентского” кода

May 19, 2015 · I have a quick question. When you’re passing tasks to WhenAll, do you have to ConfigureAwait(false) on all of them before passing them, or is it enough to ConfigureAwait(false) only on the task returned by WhenAll? · The call to ConfigureAwait(false) method is only necassary when you await a method and don’t need to sync back to or capture the

How to use Task.WhenAll() to await multiple concurrent tasks Aug 13, 2012
WhenAll and exception Jan 24, 2011


David Pine pinged me on Slack the other day, suggesting that I write a blog post about the SynchronizationContext in ASP.NET Core. So, here it is! There Isn’t One. My inital reply was just “well, that would be a short post!” Because there isn’t a SynchronizationContext in ASP.NET Core.. Why No SynchronizationContext?

Nov 02, 2010 · Is this enough? My gut feeling is that this will give enough control over the flow of the application if:. The defaults in TAP are chosen appropriately so that the easiest way of starting a computation is also an easily “top-down-configurable” one

This lightweight tool uses the .NET Compiler Platform (“Roslyn”) to analyse and fix any code that awaits tasks without configuring them first, with an aim to reduce ambiguity by always specifying whether the calling context is needed, as well as to reduce the number of deadlocks when context is not needed.

ConfigureAwait FAQ An Introduction to System.Threading.Channels Welcoming Oren Novotny as the new Executive Director of .NET Foundation Event Driven Collaboration – Ian Cooper What You Need to Know About Open Source – Trust Me, I’m a Lawyer – Jeff Strauss

Jun 21, 2013 · Since you’re not using async/await, you don’t need to worry about the ConfigureAwait call. It would only be required if you used await against the result, as the “await” state machine is what attempts to get the context, etc.

Oct 30, 2017 · Lately we had a discussion on when to use ConfigureAwait(true) or ConfigureAwait(false) in ASP.NET Core 2. In the end most of the team, including me, had a faulty assumption on how to do this in ASP.NET Core. In this case ASP.NET Core is different from ASP.NET. Good to know if you have to decide on what

I followed the Visual Studio suggestion to install “Microsoft.CodeAnalysis.FxCopAnalyzers” and suddenly I get tons of new warnings. One of them is:

As my knowledge when we using ConfigureAwait(false) the rest of async method will be run in the thread pool.. Close, but there is an important caveat you are missing. When you resume after awaiting a task with ConfigureAwait(false), you will resume on an arbitrary thread.Take note of the words “when you resume.”. Let me show you something:

OK I’ve done some experiments and can answer (to a certain extent) my own question. The fact that the called method is async and that we have ConfigureAwait(false) chained to it is irrelevant in this case, because it’s being called without await and will therefore run synchronously.; I misunderstood the C# calling mechanism.

Стратегия, когда библиотечный код полностью покрывается ConfigureAwait(false), изменяет поведение по умолчанию, и, что более важно, такой подход лишает разработчиков “клиентского” кода

を呼び出すだけ。 Delay(1)は必ず(?)スレッドプールスレッドで実行され、そしてConfigureAwait(false)することで、UIスレッドに戻ってこないようにする、という仕組み。 背景. await した task は必ずしもスレッドプールスレッドで実行されるとは限らない。 MSDNのどこかにもそんなことが明記されていた

近日来,涌现了许多关于 Microsoft .NET Framework 4.5 中新增了对 async 和 await 支持的信息。 本文旨在作为学习异步编程的“第二步”;我假设您已阅读过有关这一方面的至少一篇介绍性文章。 本文不提供任何新内容,Stack Overflow、MSDN 论坛和 async/await FAQ 这类在线资源提供了同样的建议。

.NET core does not have synchronization context. Therefore no need to bother about setting ConfigureAwait(false) ASP.NET Core does not have a synchronization context, but .NET Core itself does have the SynchronizationContext base class and related infrastructure..NET Core is often treated synonymously with ASP.NET Core since that is the main use case, but 3.0 brings the WPF/WinForms

David Pine pinged me on Slack the other day, suggesting that I write a blog post about the SynchronizationContext in ASP.NET Core. So, here it is! There Isn’t One. My inital reply was just “well, that would be a short post!” Because there isn’t a SynchronizationContext in ASP.NET Core.. Why No SynchronizationContext?

I get in a lot of fights. Fights about async/await anyway. Despite async/await being over 5 years old (AOTW), there still remains a lot of confusion regarding some basic functionality. I do not presume to be an in-depth expert. Some of the things I read from Stephen Cleary or Jon Skeet make my eyes go

6. Libraries should consider Task.ConfigureAwait(false). This is another micro-optimization you can use to reduce your methods’ impact on the UI thread. Consider this if your library routine might be

Nov 02, 2010 · Is this enough? My gut feeling is that this will give enough control over the flow of the application if:. The defaults in TAP are chosen appropriately so that the easiest way of starting a computation is also an easily “top-down-configurable” one

When we use async/await, we rarely need .then, because await handles the waiting for us. And we can use a regular try..catch instead of .catch.That’s usually (not always) more convenient. But at the top level of the code, when we’re outside of any async function, we’re syntactically unable to use await, so it’s a normal practice to add .then/catch to handle the final result or falling

For projects that support PackageReference, copy this XML node into the project file to reference the package.

私はConfigureAwait(false)で非同期ライブラリメソッドを呼び出しています。しかし、私はまだデッドロックで終わる。 (ASP.NETコントローラAPIで使用しています) しかし、同じメソッドをTask.Run()にラップすると、正常に動作します。 ライブラリメソッドがConfigureAwaitを内部的に使用していない

In the previous guide in this series we saw why Task.Run is mainly useful for CPU-bound code. In exploring that topic it became clear that, although you can use Task.Run with other types of operations, it may not be the best use of system resources. We also saw how easy it is to await a call to Task.Run.But that’s certainly not all there is to it.

About the author: David Boike is a developer at Particular Software who used to forget to use ConfigureAwait at least once per week until he found the tooling to handle that for him.

Subscribe C# Async Tips & Tricks 04 October 2017 on async, csharp, c#. The following are few tips and tricks for working with async in C#. This is as much a reference for myself as anyone else, but I figured it would probably useful for others as well.

Apr 12, 2012 · From time to time, I receive questions from developers which highlight either a need for more information about the new “async” and “await” keywords in C# and Visual Basic. I’ve been cataloguing these questions, and I thought I’d take this opportunity to share my answers to them.

Nov 11, 2014 · Repeat after me, “Avoid async void!”(Now say that ten times fast!) Ha ha ha. You sound funny. In C#, async void methods are a scourge upon your code. To understand why, I recommend this detailed Stephen Cleary article, Best Practices in Asynchronous Programming.In short, exceptions thrown when calling an async void method isn’t handled the same way as awaiting a Task and will crash the

Jul 10, 2019 · Did you know that the .NET compiler turns our async methods into classes? And that .NET adds a try/catch block to each of these classes, potentially hiding thrown exceptions? It’s true! In this

Nov 25, 2015 · Sometimes, we use new technologies while we are not aware of the bottlenecks and weird parts of that technology which eventually might trap us in bad situations like deadlocks which may be really hard to track. What exactly happens in Task-based Asynchronous Pattern (TAP), what are the improvements

Nowadays, Asynchronous programming is very popular with the help of the async and await keywords in C#. When we are dealing with UI and on button click, we use a long running method like reading a large file or something else which will take a long time, in that

Haven’t you shot yourself in the foot yet with async/await? If not, you are about to if you are writing a client library for your newly created ASP.NET Web API application with .NET 4.5 using new asynchronous language features. Filip Ekberg also has a very nice and useful blog post which has an

await後の処理を呼び出し元のコンテキスト(スレッド)とは異なるコンテキストで呼び出すには、ConfigureAwait()メソッドを呼び出し、引数(continueOnCapturedContext)にfalseを与えます。 コード例

Return the task. For high-throughput scenarios and if there are only one or two asynchronous exit points in the Handle method, the async keyword can be avoided completely by returning the task instead of awaiting it. This will omit the state machine creation which drives the async code and reduce the number of allocations on the given code path.

Nov 03, 2014 · Hi, I’ve read somewhere that it might be a good idea for libraries to use ConfigureAwait(false) if it uses any async methods internally. I’m not sure I understand fully this, so I thought I’d post