Microsoft .NET Code Analysis: Recognizing the Significance of ConfigureAwait in Reusable Assemblies

Mar 21, 2024 10:23 AM

In the context of reusable assemblies that involve asynchronous operations, it is crucial to emphasize the usage of ConfigureAwait(false) within DLLs. Surprisingly, the codebase I examined for this chapter did not employ ConfigureAwait when handling any of their asynchronous calls. Let’s consider an illustration from my project Spargine, to shed light on this issue:

await request.Body.CopyToAsync(ms, CancellationToken.None).ConfigureAwait(false);

Here are more reasons why ConfigureAwait() should be used and how:

1. Performance improvement: By default, when an await expression is encountered, the current synchronization context is captured, and the continuation after the async operation is scheduled to run on the same context. This behavior can be beneficial in GUI applications, but in other scenarios, such as server-side applications or CPU-bound work, capturing the synchronization context can introduce unnecessary overhead. By using ConfigureAwait(false), you can avoid the overhead of capturing and restoring the synchronization context, leading to potential performance improvements.
2. Avoiding deadlocks: When an async method resumes on the captured synchronization context, it expects the context to be available. If you’re awaiting an async operation within a context (e.g., in a UI event handler), and that operation also relies on the same context, it can result in a deadlock. This situation often occurs when using Task.Wait or Task.Result in combination with await. By using ConfigureAwait(false), you can explicitly state that you don’t need the original synchronization context, which helps prevent potential deadlocks.
3. Scalability: In scenarios where there’s limited availability of synchronization contexts, such as in highly concurrent applications, using ConfigureAwait(false) can help improve scalability. Since capturing a synchronization context may lead to serialization of execution, releasing the context can allow the async operations to execute on different threads concurrently, resulting in better overall performance.

For asynchronous calls in GUI applications, it is advisable to use ConfigureAwait(true) to ensure that the execution continues on the UI thread.

When I setup the ASYNC0004 code analysis in my .editorConfig it looks like this: dotnet_diagnostic.ASYNC0004.severity = error

Summary

While reviewing the codebase for this recommendation, I identified a total of over 1,400 instances in their code that ConfigureAwait() was not being used. For more information go here: https://devblogs.microsoft.com/dotnet/configureawait-faq/

For further guidance and insights, I highly recommend obtaining a copy of my book, “Rock Your Code: Coding Standards for Microsoft .NET” available on Amazon.com. Additionally, to explore more performance tips for .NET, I encourage you to acquire the 3rd edition of “Rock Your Code: Code & App Performance for Microsoft .NET” also available on Amazon.com.

To analyze your code using the same settings I used in these articles, I encourage you to incorporate my EditorConfig file. It can be found at the following link: https://bit.ly/dotNetDaveEditorConfig. I update this file quarterly, so remember to keep yours up to date as well. I hope you will check out my OSS project Spargine by using this link: https://bit.ly/Spargine.

Please feel free to leave a comment below. I would appreciate hearing your thoughts and feedback.

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