Global MVVM ViewModel in UWP app

Question

In WP8.1 or WPF desktop apps I could create my ViewModel as a static instance in App.xaml.cs and refer to it throughout the app as "App.myViewModel" but in UWP that does not seem to work (perhaps by design?).

The reason I want a global ViewModel is that, like many apps, I have one main page that populates the VM by downloading info from websites (I'm working on a business based RSS Reader for a client) and when I navigate to another page then come back to MainPage my vm is empty again (as I appear to have no option but to declare it in MainPage) so I have to reload all the data every time.

Also if I want to access the VM from navigated pages I now have to pass a reference to the VM through to that page whereas with the global approach I could still access App.myViewModel.

The only time I alter the VM contents is from UI actions on the Mainpage so I just want to be able to navigate back to the main page from other pages and have the VM still intact.

Can someone please explain how this is done in UWP? Can I still use App.xaml.cs and if so, how? If this is not possible why was it designed like this?

Even though it is an anti pattern, you could use a singleton for your VM. That way you will never lose any info. — Nahuel Ianni, May 02 '16 at 07:44

score 1 · Accepted Answer · edited May 23 '17 at 12:31

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You are looking for ViewModelLocator. Here you have nice explanation and example how to use it. https://stackoverflow.com/a/14154088/4727426

edited May 23 '17 at 12:31

Community

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answered May 02 '16 at 09:34

matihuf

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Thanks for the answer but that means I have to refactor my app to use MVVMLight which I'd rather not - is there an equivalent just using normal MVVM structures? – nzmike May 02 '16 at 09:52
Did some more research and it really looks like MVVMLight is the best solution so I have marked this as the answer. – nzmike May 03 '16 at 22:59

Global MVVM ViewModel in UWP app

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