WPF/MVVM - how to execute commands on start-up?

I'm writing a WPF app following MVVM principles.

I wan't to execute a command on startup - I'm in doubt as to what is the best method?

The ViewModel should be indifferent as to whether there are any views, right?

Is it then 'ok' to do stuff as the last thing in VM constructor? Or is there an event for 'application is now up and running, all initialization has completed' that I can hook onto?

It feels wrong to wire it into the view model?

To be a bit concrete, I'd like to do as Visual Studio and load 'most recent solution' if the user has selected that in preferences. If the user manually loads a solution through GUI I start the flow in a MainFormViewModel and I could handle the load in last li开发者_StackOverflow社区nes of constructor there?

Any thoughts?

Anders, Denmark

The Windows.Interactivity approach or asynchronously loading their preferences from the constructor are equally viable - an alternative exists if your using the MefedMVVM framework.

You can also import the IContainerStatus to attach to the view being loaded entirely from the view model (and therefore nothing to forget doing in the XAML) More info is available here

I really wanted to avoid calling methods from within the ViewModel constructor - and in my view activating events from constructor is doing just that (or at least when using Prism as I am (should have mentioned that).

I ended up doing the simple thing and simply calling a Loaded method on my main ViewModel after construction has ended.

Nonetheless, Scott singled out as the answerer - thank you all for taking the time. I appreciate your point of view even if I chose another way in the end.

Anders, Denmark

        var mainViewProvider = ObjectFactory.GetInstance<IMainViewProvider>();
        var mainWindowViewModelProvider = ObjectFactory.GetInstance<IMainWindowViewModelProvider>();

        var mainWindow = mainViewProvider.GetView();
        var mainWindowViewModel = mainWindowViewModelProvider.GetViewModel();
        mainWindow.DataContext = mainWindowViewModel;

        mainWindowViewModel.Loaded(Settings.Default.LoadLatestOnStart);

        mainWindow.Show();

What you can do is use your MainForm's (the one which needs to load the solution) Loaded event.

Use Windows.Interactivity EventTrigger to attach a command to Loaded event. And on that command's execution, load the solution.

I would introduce Controllers which are responsible for the UI workflow. They know when the application has started and they can execute Commands. This doesn't violate with the MVVM pattern. If you are interested how this work then you might find the sample applications of the WPF Application Framework (WAF) interesting.

That's ok if and when you setup the context in code, but not if you do it from xaml - for the sake of transparency and flexibility one should consider supporting both code and xaml.

Another approach could be to trigger something on your model from xaml when certain criteria has been met.

I believe a storyboard could be used for this approach.

/Torben Falck, Strongminds, Denmark, www.strongminds.dk