thank you, this approach works.
To be honest, I have tried almost the same code before I posted my question here...
The only flaw is that all events from the initialization sequence of the application are beeing send to default PRISM Logger (the logger created in the CreateLogger method). And my logger kicks in after the "Initializing shell" event.
Is there any chance that my Logger (with EventAggregator support) could be used for the events from the Initialization sequence?
I guess not because I can't compose my Logger before the MEF container is available, but I am asking anyway...