ConfigureAwait FAQ - .NET Blog Without a lock, 2 threads might enter the critical section, ending up with 2 instances of our Singleton. By adding ConfigureAwait (false), which tells the compiler explicitly to NOT use the calling context to schedule callbacks, the continuation will not be entered onto the original queue, but rather some other thread in the thread pool This will avoid the deadlock. Deadlock example 1: The Nested-Lock Otherwise, the consumers of your library may face deadlocks by consuming your asynchronous methods in a blocking fashion. This is important because a deadlock will freeze an application and will result in a bad . Async Wandering Part 8 — async and await — the biggest C# ... Be especially careful when using synchronous operations like Dispatcher.Invoke and task.Wait() Use async/await if possible. C# Language Tutorial => ASP.NET Configure Await In this case, you can replace WebClient with the more async-friendly HttpClient and get this to work on the desktop, as shown in Figure 6. As you can see, the author of that article used one single method to avoid deadlock. You would have to use ConfigureAwait(false) for every await in the transitive closure of all methods called by the blocking code, including all third- and second-party code. It changes the way we write applications and gives a lot of advantages. c# - Stored Procedure deadlocking when running Tasks ... That was just two simple drawings. This is the eighth part of the Async Wandering series. What happens is that the main thread will call the async method, and you end up blocking this thread until that async method is complete. The recommendation is to apply these solutions together for best . We'll also cover why you need to use ConfigureAwait(false) in all of your library code to help protect the consumers of your code from encountering deadlocks and other threading issues. Web apps also validate the ID tokens. What ConfigureAwait(false) does is create an awaitable that does not run the continuation of the awaited task on the previous synchronization context. async/await. I'm using ASP.NET MVC, .NET Framework version = 4.7.2. From what I've read, you can use that when you don't want it to run in the calling context, and this can be useful to prevent deadlocks, but I can't see any potential deadlock if ConfigureAwait (false) wasn't used here. //async句をつけたメソッドはAsyncのsuffixを付けることが推奨されています。. 0 comments. Here's my order, but don't go anywhere — you go tell the kitchen what to do, and come straight back here you hear me! Consider Figure 3 again; if you add "ConfigureAwait (false)" to the line of code in DelayAsync, then the deadlock is avoided. I just finished The zen of async: Best practices for best performance talk of Stephen Toub's on //Build and learnt how easy is to end up with a deadlock while writing asynchronous code with new C# 5.0 language features (AKA async/await). I find that inserting into the actual table is what is causing the deadlock. The blocking hack requires your team to have strict discipline. GetLeftPart (UriPartial. So, what I have to recommend you is to avoid at all cost using ".GetAwaiter ().GetResult ()", ".Result" or ".Wait ()". June 4, 2020 ~ afish. In the first case, this context is a UI context (which applies to any UI except Console applications).In the second case, this context is an ASP.NET request context. SynchronizationContext.Post(..). If you don't, you will have an instant deadlock. In this case, you can replace WebClient with the more async-friendly HttpClient and get this to work on the desktop, as shown in Figure 6. The only reason for ConfigureAwait(false) is to prevent single-thread synchronization context from deadlock, which is the case for GUI frameworks like WinForm/WPF. What Causes the Deadlock. Protected web APIs need to validate access tokens. Such deadlocks can be solved by using .ConfigureAwait(false) or removing the blocking waits and making the whole call stack async. Well, ConfigureAwait method is used to configure an awaiter of Task on which we are using configuration. So basically my await calls should change from: await NavigationService.NavigateAsync . How to fix violations To fix violations, call ConfigureAwait on the awaited Task. The best approach is not to rely on it, just don't mix synchronous and async calls, let Async/Await propagate. This can also reduce impact on the UI thread and prevent deadlock . 67% Upvoted. Token Validation has multiple parts, checking whether the token belongs to the application, has been issued by a trusted Identity Provider (IDP), has a lifetime that's still in range and hasn't been tampered with. It is simply a method that returns a struct (a ConfiguredTaskAwaitable) that wraps the original task it was called on as well as the specified Boolean value. ConfigureAwait的使用 Task.ConfigureAwait(bool)指示了Awaiter完成任务时是否尝试将结果返回原上下文中继续执行，Ture为尝试返回，False则相反。 在讨论ConfigureAwait的正确使用场景之前，则应该先了解SynchronizationContext类型。 SynchronizationContext SynchronizationContext提供了在同步模型中传播上下文的基本功能，其中Send . MMALSharp is a library I maintain for the Raspberry Pi camera module. If you want, I could still turn my original code into a running example, but I highly doubt it will ever reproduce the deadlock. . using (var client = new HttpClient ()) {var baseUrl = Request. Hint: you'll get a threading exception. To fix this issues you need to use ConfigureAwait(False) which will make Line 5 and any other code below "await" to run without using the httpContext. WebClient uses the older event-based asynchronous pattern (EAP), which always captures the context. Let's say you have: var food = waiter.BringFoodAsync(myOrder).Result; This is basically saying: "Hey waiter! It was created to free up Processing power while we wait for a non CPU based task to complete. I just want to know if the recommendation is "if you get TCS deadlock issues, the recommendation is to upgrade to 4.6.2". As mentioned above, in library code, it is recommended to use ConfigureAwaiter(false) for each await for asynchronous operations. ConfigureAwait analysis. By the end of this session we will understand what SynchronizationContexts are, when to use ConfigureAwait, how deadlocks occur and how to detect and avoid them. ConfigureAwait (false)有以下好處. I have a public async void Foo() method that I want to call from synchronous method. 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 far all I have seen from MSDN documentation is calling async methods via async methods, but my whole program is not built with async methods. After the I/O thread is done, it dispatches the rest of the DoSomeWorkAsync method to the thread the method was called by. . ViewBag.Title = GetAsync ().Result; // This cause deadlock even with "ConfigureAwait (false)" ! on thread 12 completing, any thread can pick up where work left off. ConfigureAwait is not used in libraries. Finally here is the stored procedure. In the code that relies on the asynchronous programming model (async/await keywords), ConfigureAwait() calls are often used to manage the synchronization context.The way ConfigureAwait() calls work and their usage scenarios are explained in detail in this Microsoft .NET Blog article as well as in many other posts that you can find on the Internet, but the usage advice . What is a deadlock? Async is one of the most popular C# features nowadays. 1.提高返回執行效能，因不需要進入queue少了排隊成本和檢查 TaskScheduler 及 SynchronizationContext額外花費. ConfigureAwait (false) means that you want the thread that picks up after the await is the same thread that started. A button click leads to a deadlock here. I don't see any framework bug here. Here is a bit more detailed explanation on the importance of ConfigureAwait method (a quote from my blog post): We will take a closer look at why we care about async, how it works and then deep dive into async issues. External Tasks and Grains. 分类于 专业技术. 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