ThreadStatic in asynchronous ASP.NET Web API

Question

Is there a possibility to use thread static like variables within a single request? The current code uses a thread static variable for logging purposes and now we want to use async controller methods (with async and await pattern) which results in problems because the variable is null when a new thread is opened.

score 14 · Accepted Answer · answered Feb 28 '17 at 14:14

14

await can cause thread jumps, so thread static variables will naturally cause problems.

To work around this, you can either use AsyncLocal<T> (available in .NET 4.6), or (if you must) HttpContext.Current.Items. Of those two, I would definitely recommend AsyncLocal<T> over Items, if it's available on your platform.

answered Feb 28 '17 at 14:14

Stephen Cleary

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Can I ask you the reason why you recommend AsyncLocal over Items? – vinhent Oct 10 '18 at 16:02
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I recommend `AsyncLocal` over `HttpContext.Current` because `HttpContext.Current` is considered a poor design and has been removed in ASP.NET Core. – Stephen Cleary Oct 11 '18 at 14:27

ThreadStatic in asynchronous ASP.NET Web API

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