StackOverflow2013

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POHow can I load my viewmodel and still get events?
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copied!<p>I'm trying to implement MVVM and in the ViewModel I'm doing some async fetching of data. For that purpose I've tried to loading data in the constructor:</p> <pre><code>MyModel Model { get; set; } public MyViewModel() { Model = new MyModel(); Model.Foo = await LoadDataFromIsolatedStorage(); </code></pre> <p>But this isnt valid as you cant append async to the contructor. So I tried a public static load function:</p> <pre><code>MyModel Model { get; set; } public MyViewModel() { Model = new MyModel(); } async public static void Load() { Model.Foo = await LoadDataFromIsolatedStorage(); </code></pre> <p>But here WP8 complains that it <code>Cannot await void</code>. Because you would set up the ViewModel and bind it to the View in the code behind of the view. Boring. Lastly a fix is making the Load function return a ViewModel, so that you in the code behind of the view can do something like:</p> <pre><code>protected override void OnNavigatedTo(NavigationEventArgs e) { MyViewModel viewModel = await MyViewModel.Load(); </code></pre> <p>with the following code to load:</p> <pre><code>MyModel Model { get; set; } public MyViewModel() { Model = new MyModel(); } async public static Task<MyViewModel> Load() { MyViewModel viewModel = new MyViewModel(); viewModel.Model.Foo = await LoadDataFromIsolatedStorage(); return viewModel; </code></pre> <p>NOW, the problem at hand is that I have no control if the data loaded should force the application to navigate to another page. Lets say MyViewModel loads a variable from isolated storage, that should then make the app navigate to another page?</p> <p>I've set up eventlistener to MyViewModel to make the app navigate, but I cant do this when I initiate it.</p> <p>Does not work with events:</p> <pre><code>protected override void OnNavigatedTo(NavigationEventArgs e) { MyViewModel viewModel = await MyViewModel.Load(); viewModel.NavigationAction += viewmodel_NavigationAction; } void viewmodel_NavigationAction(sender, args) { NavigationService.Navigate(...) } </code></pre> <p>Would work but I "cannot await void":</p> <pre><code>async protected override void OnNavigatedTo(NavigationEventArgs e) { MyViewModel viewModel = new MyViewModel(); viewModel.NavigationAction += viewmodel_NavigationAction; await viewModel.Load(); // given the Load only is a async void and not Task<T> } void viewmodel_NavigationAction(sender, args) { NavigationService.Navigate(...) } </code></pre>

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