IHostApplicationLifetime never invoke shutdown callbacks in WinUI templates

[katdti]

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Describe the bug

Callbacks on the IHostApplicationLifetime interface is never invoked when the App is closed.

To Reproduce

1. Create a service that uses IHostApplicationLifetime

public class DummyService
{
    public DummyService(IHostApplicationLifetime hostApplicationLifetime)
    {
        hostApplicationLifetime.ApplicationStopping.Register(() =>
        {
            // This code is never called
        });
    }
}

2. Configure service in app.xaml.cs

        .ConfigureServices((context, services) =>
        {
            services.AddSingleton<DummyService>();
        }

3. Run the App and close it
4. Result: The registered callback is never called and any background services added with services.AddHostedService<MyHostedService>(); is never started.

Additional context

No response

Applies to the following platforms:

• [X] WinUI
• [ ] WPF
• [ ] UWP

About your setup

• Visual Studio Version: 17.2.5
• Template Studio Wizard Version: 5.1
• Windows Build: 19044

[mikebattista]

I believe these events are only raised if you use Start/Stop/Run on the Host to control the application lifecycle, which the templates do not.