[Navigation] Variation in the shell page .xaml mark up, influence whether a shell pages and shellModel ctors are called.

[MarkAllan007]

Current behavior

Expected Behavior

How to reproduce it (as minimally and precisely as possible)

Environment

Nuget Package (s), Package Version(s):

Affected platform(s):

• iOS
• macOS (AppKit)
• Mac Catalyst
• Android
• WebAssembly
• Windows
• Skia (WPF)
• Skia (GTK on Linux/macOS/Windows)
• Skia (Linux Framebuffer)
• Build tasks

Visual Studio:

• 2019 (version: )
• [X ] 2022 (version: )
• Visual Studio Code (version: )
• Rider Windows (version: )
• Rider macOS (version: )

Relevant plugins:

• Resharper (version: )

Anything else we need to know?

[MarkAllan007]

Current behavior

Create a Uno app using the wizard. Include WinUI 3, WASM and GDK. Presentation MVUX, Xaml, any Theme. DI, Config, HTTP, Localization. ToolKit, Server, PWA M, CPM, Serilog or Default.

The Shell page .xaml should contain the markup to load the Uno Logo screen. Compile this app, place a break in the ShellModel ctor or run the app.

On launching the app, the ShellModel ctor should be called.

Replase the Shell page .xaml mark up with grid and text controls to display "Hello World!". Comment out the references to ContentControl. Put a break in the ShellModel ViewModel ctor. Compile and run the app. The ShellModel ctor is not created /instanciated.

Expected behavior

Both the Shell and ShellModel ctors should be called. The Shell pages .xaml mark up should not stop the ShelModel ctor from being instanciated, yes?

The ShellModels ctor is not called.

Thanks,
Mark Allan

[nickrandolph]

Hi @MarkAllan007
We need to document the behaviour of Shell but essentially it needs to implement IContentControlProvider which means it needs to return a ContentControl where the navigation for the application will take place.
It's also worth nothing that unlike other pages/viewmodels, the shell viewmodel is actually closer to a service as it is a singleton that is useful for registering application lifecycle events, rather than for data binding to in the shell
I'm going to leave this issue open for now so that we ensure this is documented for Navigation.

[xperiandri]

In our case we have multiple shells depending on user role