Using data from a ViewModel in a ModalDialog even though it lives in the Shell

Question

I'm writing a UWP and using Template 10.

I've created a ModalDialog that should show the user some data that was just calculated in a ViewModel.

Here's where I'm lost:

#1, the ModalDialog needs data from my ViewModel. #2, the ModalDialog needs to call 1+ method(s) on the ViewModel depending on which button the user clicks.

My Shell.xaml.cs:

public sealed partial class Shell : Page
{
    public static Shell Instance { get; set; }
    public static HamburgerMenu HamburgerMenu => Instance.MyHamburgerMenu;


    public Shell()
    {
        Instance = this;
        InitializeComponent();
        if (App.MobileService.CurrentUser == null)
            LoginModal.IsModal = true;
    }

    public Shell(INavigationService navigationService) : this()
    {
        SetNavigationService(navigationService);
    }

    public void SetNavigationService(INavigationService navigationService)
    {
        MyHamburgerMenu.NavigationService = navigationService;
    }

    #region Login

    private void LoginLoggedIn(object sender, EventArgs e)
    {
       MyHamburgerMenu.NavigationService.Navigate(typeof(Views.MainPage));
       LoginModal.IsModal = false;
    }

    #endregion
}

}

Shell.xaml

<Controls:ModalDialog x:Name="ScoreModal" Grid.RowSpan="3"
                          CanBackButtonDismiss="False"
                          DisableBackButtonWhenModal="True">
        <Controls:ModalDialog.ModalContent>
            <myControls:QuizScorePart
                    HorizontalAlignment="Stretch" VerticalAlignment="Stretch"/>
        </Controls:ModalDialog.ModalContent>
    </Controls:ModalDialog>

What I've tried:

I tried just putting the control for the ModalDialog in the View that uses the ViewwModel I wish to speak to, but that doesn't work; that view lives inside the shell, meaning everything underneath the ModalDialog is NOT disabled. It HAS to be in the Shell, from what I know.

I tried setting up a method in the Shell.xaml.cs file that sets IsModal for my dialog to true/false; this works, but it doesn't solve my problem of interacting with my ViewModel.

I'm lost. Thanks anyone for the help.

Answer 1

reference the Search example, there are delegates to handle in the actual part, look at the codebehind for the LoginPart....

What I specified below in comments is how I do it with a LoginPage, not a usercontrol. Which has a LoginPageViewModel which in-turn has a the SettingsService instance referenced.

Edit

Think of it this way...ScoreModal isn't anything other than another view control. QuizScorePart is your View, I assume that QuizScorePartViewModal exists. From there it becomes a message passing exercise between viewmodels. At least that is what I see after the last comment. You need to know what the user clicked on button wise. Assuming that the above is true, then QuizViewModel would react to that message it was listening for. Shell is merely a holding location for a complete screen cover for the it only reacts to IsModal. If that is an issue consider a Service to hold the button selection, similar to how SettingsService works. Nothing says that QuizScorePart couldn't have its datacontext set to that of the QuizViewModel, but it might be a testing issue at that point.