Async call to the WCF service doesn't preserve CurrentCulture

Question

According to the answer in this question async/await call should preserve CurrentCulture. In my case, when I call my own async methods, the CurrentCulture is pr

Answer 1

Resetting culture back to what it was before the await is usually the job of the synchronization context. But since (as far as I understand it), you don't have any synchronization context, the await won't modify the thread culture in any way.

This means that if you're back on the same thread after await, you're going to see the culture that you set. But if you resume on a different thread, you will see the default culture (unless somebody else modified it for that thread too).

When are you going to be on the same thread after an await, when there is no synchronization context? You're guaranteed to be on the same thread if the async operation completes synchronously (like your GetIntAsync()), because in that case, the method just synchronously continues after the await. You can also resume on the same thread if you're lucky, but you can't rely on that. This can be non-deterministic, so your code might seem to work sometimes, and sometimes not.

What you should do when you want to flow culture with awaits and you don't have a synchronization context that does it for you? Basically, you have two options:

1. Use a custom awaiter (see Stephen Toub's WithCulture(), as linked by Noseratio). This means that you need to add this to all your awaits where you need to flow the culture, which could be cumbersome.
2. Use a custom synchronization context that will flow the culture automatically for every await. This means you can set up the context only once for each operation and it will work correctly (similarly to what ASP.NET synchronization context does). This is probably the better solution in the long run.