CallContext vs ThreadStatic

Question

What are differences between CallContext and ThreadStatic?

I've understood that in an ASP.NET environment data stored in CallContext could be persisted throughout the request until it ends while ThreadStatic may or may not work since the request may switch threads. I've also learned that the HttpContext is internally stored using the CallContext.

In a regular application they both seem to persist throughout the same thread call. When isn't this the case?

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Edit: In the comments I learned that the call context is an abstraction over a thread static store. The ASP.NET framework explicitly moves the data from one thread to the next that is to handle one request. Other framework that wants to provide thread agility could do the same to for contextual storage.

Answer 1

Very often a request will use the same thread throughout, but it certainly won't always be the case - ASP.NET exhibits thread agility. There's a really useful discussion about this on the Spring.NET forums. This refers to an in-depth blog article about the matter. I suspect that goes into more details than you'll get here :)

What conflicting information did you see, out of interest?

Answer 2

Items stored as ThreadStatic are available to more than one request. IIS reuses the thread after a request is complete to process subsequent requests. ASP.Net clears down the CallContext after each request.

Answer 3

i am also intereted in the answer about wcf service hosted in iis. i want to create , static class that will hold env. information to be used by the methods called from the main wcf method, without the need to pass it from method to method