What purpose does the InstanceContext serve with Duplex service callbacks?

When using the DuplexFactory its actually possible to directly pass the callback handler, and skip the InstanceContext wrapper. Why then would you ever use the InstanceContext for your cal开发者_如何转开发lback handler?

I am looking for real world examples of how you would use the InstanceContext. It bugs me that I can see it in the API but its not explained anywhere how it adds value, or enables new scenarios.

This might help you - link

The link tells that... "Actually, the WCF Instancecontext class is just a wrapper over the underlying instance that implements the callback interface. So if you want to reuse/share the InstanceContext between multiple client proxies, you need to keep reference to the certain object that implements the callback interface. Thus, whenever you need to create a new client proxy of the duplex service(that need a callback instanceContext), you can just construct a new one with the existing class instance that implements the callback interface."