Question

im developing a silverlight 3 beta navigation application, so i’ve gone with a slight variation of the MVVM pattern 🙂 (all-in-one viewmodel), using prism, and stuff.

Question: How do i navigate to a different “NavigationPage” in the viewmodel

Now to cut a long story short, the viewmodel is declared as a page resource.

<navigation:Page.Resources>
    <mvvm:LoginModel x:Key="DataSource" d:IsDataSource="True"></mvvm:LoginModel>
</navigation:Page.Resources>

And then a command is used to wireup everything with the viewmodel

<Button x:Name="LoginButton" Width="100"  Margin="8" Content="Login"
        prism:Click.Command="{Binding LoginCommand}"/>

Now if i try to navigate anywhere in the viewmodel like so

this.NavigationService.Navigate(new Uri("/Views/About.xaml", UriKind.Relative));

the Navigationservice is null, i’ve looked around and found this article, which describes using helix 0.3 for navigation, this was built back in the sl2 days, when the navigation controls never existed, now helix’s model works well, and by implementing INavigationAware in the viewmodel, you are able to gain access to the NavigationContext, and then do whatever it is you require, i have tried helix, and it works.

SL3 comes with the builtin Navigation support, so to speak, which does exactly what helix does. So i dont wanna use a 3rd party framework, instead i prefer to use the built in sl3 features.

Is there anything in SL3 that emulates the helix’s INavigationAware interface?

Answer 1

I personally think NavigationService is a UI-concept associated with the UI Frame or Page.

Another way to accomplish this without having to pass in a NavigationService into the view model is to have the ViewModel raise an event when navigation is supposed to occur… have the view handle the view model event and call Navigate in response.