Thank you for the fast answer. So what I'm doing ... IMO nearly nothing. I just replaced the usercontrol for the view with Fluent:RibbonWindow as it was the answer by Bladewise some months ago. So my code is identical to the tutorial at www.mindscapehq.com, just the AppView type changed.
Found another post https://caliburnmicro.codeplex.com/discussions/268425, unfortunately the bootstrapper code isn't shown here and using this code with the tutorial bootstrapper leads to the same exception.
René
Found another post https://caliburnmicro.codeplex.com/discussions/268425, unfortunately the bootstrapper code isn't shown here and using this code with the tutorial bootstrapper leads to the same exception.
René