Application

Tip

This article covers Uno-specific information for Microsoft.UI.Xaml.Application. For a full description of the feature and instructions on using it, see Application Class.

• The Microsoft.UI.Xaml.Application class enables an application to manage the lifetime of the application and to query the application's state.

Lifecycle events

Suspending, Resuming, EnteredBackground and LeavingBackground are not members of Microsoft.UI.Xaml.Application, matching the Windows App SDK. Subscribe to the events of the same names on Windows.ApplicationModel.Core.CoreApplication instead:

using Windows.ApplicationModel.Core;

CoreApplication.Suspending += OnSuspending;

private void OnSuspending(object? sender, SuspendingEventArgs e)
{
    var deferral = e.SuspendingOperation.GetDeferral();
    //TODO: Save application state
    deferral.Complete();
}

Which targets report suspension follows the platform:

Target	Reports suspension
Android, iOS, tvOS	Yes — the OS genuinely backgrounds and may terminate the app.
Skia Desktop (Windows, macOS, Linux)	No. Desktop apps have no suspended state, as on the Windows App SDK. Save state from Window.Closed.
WebAssembly	No.

Limitations

Android, iOS and tvOS

The handler cannot perform asynchronous work: the deferral must be completed before the handler returns, because the OS gives the app only a short, non-extendable window before it is suspended.