MVVM light Page Navigation Outside ViewModel

Question

I'm trying to Invoke NavigateTo in Windows 8.1 Universal app outside of the wiew model. I already tried:

var dispatcher = Window.Current.Dispatcher;

await dispatcher.RunAsync(
    CoreDispatcherPriority.Normal, 
    async () => await NavigateToRegistrationPage()
);

Resulting with exception thrown

Object reference not set to instance of object.

I also tried Using Messenger to invoke navigation form ViewModel via messenger message:

Messenger.Default.Send<MessengerEvents.NavigateToRegistrationPage>(
    new MessengerEvents.NavigateToRegistrationPage()
);

Public LoginViewModel //...

MessengerInstance.Register<MessengerEvents.NavigateToRegistrationPage>(
    this,
    (message) => GoToRegistrationPage()
);

Doesn't work either.

Error has been thrown by the target of invocation

I cant invoke navigation directly in viewmodel (checked without messenger called directly from the view model works perfectly) as navigation is performed in response to server message.

private void GoToRegistrationPage() 
{
    NavigationService.NavigateTo(ResourceService.CHOOSE_REGISTRATION_PAGE); 
}

Depending on how you are using MVVM-Light, there should be an IOC container from which you can request the current instance of the navigationservice. And use that to do the same actual navigation as inside your viewmodels — Depechie
ServiceLocator.Current.GetInstance<INavigationService>(); would be the code most likely — Depechie
@Depechie When i tried this i checked that i get the object but "currentPageKey" is null" I have this page in CreateNavigationService navigationService.Configure(ResourceService.CHOOSE_LOGIN_PAGE, typeof(LoginPage)); still no idea how to solve it instance.currentPageKey threw exception of type System.NullReferenceException — Groth
Hmm a bit unclear what is going on just by reading this comment — Depechie

Groth Groth · Accepted Answer · 2015-09-16T14:32:29

Problem solved, I tried to grab dispatcher from MVVM Locator, moved dispatcher to app.xaml.cs and works perfectly

MVVM light Page Navigation Outside ViewModel

1 Answers