Sorry, to keep you out of the discussion. Sacha could find the problem. Here are his findings:
The problem is that the Cinch IUIVizualiser service is trying to set a Owner Window using the Application.Current.MainWindow;
Which in your case throws this Exception “Cannot set Owner property to a Window that has not been shown previously.”
Due to the fact that your MainWindow is no longer shown and it more of a NotifyIcon. To be honest this is strange case.
To fix it, what I think you need to do, is grab a copy of the Cinch IUIVisualizer service and make your own new interface/implementation
based on it, but do not set the owner, or adjust the interface/service implementation such that you can set whether you want an owner to be set when you call ShowDialog().
This does mean you will not longer be able to use the Cinch.Bootstrapper or the [PopupNameToViewLookupKeyMetadata]
attributes, as these both assume they will be writing to the default Cinch IUIVizualiser service.
Thinking about it, you could also swap out the default Cinch.Bootstrapper, and make that write to your own version of the IUIVizualiser
Anyway there you have it, it is down to your MainWindow no longer being Shown when you try to set owner.
I’ll amend default Cinch IUIVizualiser service to allow SetParent to be set from ViewModel call, but this wil be done when
I have enough changes to warrant a new release.