Navigated event on IRegionNavigationService not firing.

[jevenson]

I have a few commands on my MainWindowViewModel that need update based on the current entry in the Navigation Journal.

I am hoping to add an event handler to the Navigated event on the IRegionNavigationService, like so

regionNavigationService.Navigated += RegionNavigationService_Navigated;

private void RegionNavigationService_Navigated(object sender, RegionNavigationEventArgs e)
{
    this.MyCommand.RaiseCanExecuteChanged();
}

The event doesn't seem to be firing though. I use the IRegionManager to navigate in my app. I checked out the Prism source code, and it looks like the IRegionManager.RequestNavigate method calls the Region's RequestNavigaiton method, which then calls the navigation logic in IRegionNavigaionService.

this.regionManager.RequestNavigate("ContentRegion", "MyView");

Any ideas on why the Navigated event isn't working for me?

[jevenson]

I found a solution to my problem.

In my MainWindowViewModel I inject the IRegionManager & IRegionNavigationService. In the view, I bind the Loaded event to a LoadedCommand, which sets the Region on the IRegionNavigationService, sets up an event handler for the Navigated event, and then navigates to the initial view of the app. Then, when viewmodels need to navigate, I get a reference to the same IRegionNavigationService from the NavigationContext parameter from the INavigationAware.NavigatedTo function.

MainWindowViewModel

public DelegateCommand LoadedCommand { get; private set; }

public MainWindowViewModel(IRegionManager regionManager, IRegionNavigationService regionNavService)
{ 
    this.regionManager = regionManager;
    this.regionNavigationService = regionNavigationService;

    this.LoadedCommand = new DelegateCommand(this.Loaded);
}

public void Loaded()
{
    this.regionNavigationService.Region = this.regionManager.Regions["ContentRegion"];
    this.regionNavigationService.Navigated += RegionNavigationService_Navigated;
    this.regionNavigationService.RequestNavigate("LoginView");
}

private void RegionNavigationService_Navigated(object sender, RegionNavigationEventArgs e)
{
   // This is the main thing I needed
    this.SomeOtherCommand.RaiseCanExecuteChanged();
}

MainWindow.xaml

<Window 
    ...
    xmlns:i="http://schemas.microsoft.com/xaml/behaviors" />

    <i:Interaction.Triggers>
        <i:EventTrigger EventName="Loaded">
            <i:InvokeCommandAction Command="{Binding LoadedCommand}" />
        </i:EventTrigger>
    </i:Interaction.Triggers>
    
    ...

LoginViewModel.cs

public class LoginViewModel : BindableBase, INavigationAware
{
    private IRegionNavigationService regionNavigationService;

    public DelegateCommand CompleteLoginCommand { get; private set; }
    
    public LoginViewModel()
    {
       this.CompleteLoginCommand = new DelegateCommand(this.CompleteLogin);
    }

    public void CompleteLogin()
    {
       this.regionNavigationService.RequestNavigate("DashboardView");
    }
    
    public void OnNavigatedTo(NavigationContext navigationContext)
    {
        // Only use the navigation service from the context, do not inject it!
        this.regionNavigationService = navigationContext.NavigationService;
    }

    public bool IsNavigationTarget(NavigationContext navigationContext)
    {
        return true;
    }

    public void OnNavigatedFrom(NavigationContext navigationContext) { }
}