Hi,
Based on my understanding the behavior you are experiencing is caused by the fact that when you navigate to a view using theRequestNavigate method of the Prism's navigation API, the navigated view will be determined based on the existing view's typeName or FullName in the specified region, and if no candidates are found a new instance of this view will be resolved from the container. In which case if you navigate to a view type that has more than one instance registered in that region only the first candidate found will be navigated to. This may be the reason why the first selected customer is displayed in your case.
For scenarios where you need to navigate to existing views or create a new one if this doesn't exist in your region, you could benefit of theIsNavigationTarget method in the INavigationAware interface. This method will be called during navigation on all views / view models (implementing this interface) in the region that are of the same type as the requested view. However, this may require passing a parameter, for example a customer id, during the navigation request in order to identify the correct view and return true or false in the IsNavigationTarget method accordingly.
For detailed information on this approaches you could check the following chapter of thePrism documentation:
In my opinion if you are using the Prism's navigation API, you could also benefit of theINavigationAware, OnNavigatedTo method to initialize newly displayed views, as for example you could use it to pass a parameter with the selected customer id, and provide the logic to set the corresponding values to the views' view models inside this method, instead of using Overrides to resolve your types.
Instead, if you want to manually create the instance of your views by using theParameterOverride option, I believe using the view injection approach instead of navigation (as suggested in the above related thread (ParameterOverride in WPF/PRISM/MVVM)) might be a more suitable approach to handle these views.
I hope this helps,
Agustin Adami
http://blogs.southworks.net/aadami