Programming WCF Services, 3rd Edition

Service Synchronization Context

The programming techniques shown so far put the onus of accessing the resource on the correct thread squarely on the service or resource developer. It would be preferable if the service had a way of associating itself with a particular synchronization context, and could have WCF detect that context and automatically marshal the call from the worker thread to the associated service synchronization context. In fact, WCF lets you do just that. You can instruct WCF to maintain an affinity between all service instances from a particular host and a specific synchronization context. The ServiceBehavior attribute offers the UseSynchronizationContext Boolean property, defined as:

[AttributeUsage(AttributeTargets.Class)]
public sealed class ServiceBehaviorAttribute : ...
{
   public bool UseSynchronizationContext
   {get;set;}
   //More members
}

The affinity between the service type, its host, and a synchronization context is locked in when the host is opened. If the thread opening the host has a synchronization context and UseSynchronizationContext is true, WCF will establish an affinity between that synchronization context and all instances of the service hosted by that host. WCF will automatically marshal all incoming calls to the service’s synchronization context. All the thread-specific information stored in the TLS, such as the client’s transaction or the security information (discussed in Chapter 10), will be marshaled correctly to the synchronization context. ...