fcbb435a_ofessional_Growth__Leadership___Description
[Title] Callbacks and Reentrancy [Category] Concurrency Management [Last Updated] 9/7/2006 [Description] 
By default WCF will not let a service callback within a service operation to its clients. The reason is that by default the service uses single-threaded access – only one client is allowed to call it at a time. If the service were to allow to call back to its client it could result with a deadlock if the client will call to the service as a result of the callback to the client. To allow callbacks, you need to configure the service for reentrancy – that is, release the lock before the callback, as show in the demo.
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