Behaviour and configuration file

Hello,

It was possible with remoting to configure CAO or SAO mode in configuration
file.

But with WCF and Instancing mode, I only found an imperative mode (i.e.
[ServiceBehavior(InstanceContextMode=InstanceContextMode.PerSession)] and no
configuration mode (app.config or web.config)

Did I miss something or is it impossible ? Indeed, configuration may break
some appplication but it was pretty useful.