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Comment by quietbritishjim | Hacker News Reader

> Do you remember ConfigureAwait(false)?

What makes you think that this no longer applies? It still does to my knowledge. The page you linked to has a section for it that just says "TBD".

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ConfigureAwait (mostly) no longer applies. You might want it in .NET 4.x apps, and in libraries that might be used in them. Or in apps with a "UI thread" - i.e. desktop GUIs.

In modern ASP .NET, it does nothing, so we don't use it.

https://stackoverflow.com/questions/42053135/configureawaitf...

Your advice is correct for ASP.NET Core (the web application framework), but not for all of .NET (Core or suffixless).

Thanks, I have edited. Even inside .NET different people work on very different things, and my niche might not be your niche.

Not even (fully) for ASP.NET Core, as Blazor Server does use a SynchronizationContext.

I actually have no idea if it still applies, but I haven't seen code that uses it for a long time. Maybe it was important for desktop apps?

It's important to have ConfigureAwait(true) (the default) any time you need the continuation to be on the same thread. This is used/needed for many UI frameworks (WPF), which is why it is the default. Otherwise you should use (false) for performance reasons.

Yes, this is very important.

I experienced deadlocks in ASP.NET Core 2.1 when I connected a legacy application to the web with it and the developers of Microsoft.AspNetCore.Mvc.Formatters.Json forgot to add .ConfigureAwait(false) to a async call into Newtonsoft.Json.

This was easily fixed by writing a small warper around the JsonInputFormatter but it shows how important ConfigureAwait is. When writing a library for anything netstandard, always put ConfigureAwait(false) after each async call where it is not mandatory to return to the same thread again.

> It's important to have ConfigureAwait(true) ... Otherwise you should use (false)

This is not universal. In modern ASP.NET core (i.e. web services), ConfigureAwait does nothing and is not recommended. I can confidently say that I don't want it in any of the code that I work on. We can make blanket statements, but clearly we do different things using different patterns and one size does not fit all.

https://stackoverflow.com/questions/42053135/configureawaitf...

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