Are WCF request handling Thread Agile?

Question

I have seen lots of documentation on how Agile Asp.Net Request handling is? I want to know is the case same with WCF Request handling. Can we rely on the fact that the Thread that starts Wcf request handling will finish it?

I am maintaining a Wcf Application where at lots of places ThreadStatic variables are used. Although the code is working but is it reliable? Is it worth changing it or should I keep it as it is?

Answer 1

When creating a WCF service you can set the threading and service instantiating behaviour, by decorating the service implementation class with a ServiceBehavior attribute:

[ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Single)]
class SingleCachingHttpFetcher : IHttpFetcher

The above code snippet is from http://msdn.microsoft.com/en-us/library/system.servicemodel.servicebehaviorattribute.concurrencymode.aspx

EDIT
I dit a bit more research and found this article: http://blogs.microsoft.co.il/blogs/applisec/archive/2009/11/23/wcf-thread-affinity-and-synchronization.aspx. It basically says that no, you cannot be sure that the same thread starting the request will be the one finishing it.

EDIT 2
This question has been discussed before at StackOverflow. It links to How to make a WCF service STA (single-threaded) where there is a description on how to create an OperationBehavior which will force a single threaded apartment. The example deals with calling GUI components, but it should work for other single threaded requirements as well.