App Close Handler

Tip

This article covers Uno-specific information for App Close Handler. For a full description of the feature and instructions on using it, see SystemNavigationManagerPreview.CloseRequested Event.

• The SystemNavigationManagerPreview API allows your app to handle or prevent users' requests to close it. This only works for standard app closing requests - the user can still kill the application's process by other means.

Supported features

Feature	Windows	Android	iOS	Web (WASM)	macOS	Linux (Skia)	Win 7 (Skia)
CloseRequested	✔	✖	✖	✖	✔	✔	✔

Using App Close Handler with Uno

• On non-supported platforms, the CloseRequested event is never raised and the application will close directly.
• To use CloseRequested on UWP/WinUI, the confirmAppClose capability needs to be declared in the application manifest. See App close confirmation in UWP blog post for a full example.
• To execute asynchronous logic, get an event args Deferral at the beginning of the event handler and complete it after the logic is finished. See below for an example.

Example

SystemNavigationManagerPreview.CloseRequested += App_CloseRequested;

private async void App_CloseRequested(object sender, SystemNavigationCloseRequestedPreviewEventArgs e)
{
    var deferral = e.GetDeferral();
    var dialog = new ContentDialog()
    {
        Title = "Exit",
        Content = "Are you sure you want to exit?",
        XamlRoot = this.XamlRoot,
        PrimaryButtonText = "Yes",
        SecondaryButtonText = "No",
        DefaultButton = ContentDialogButton.Secondary
    };

    if (await dialog.ShowAsync() == ContentDialogResult.Secondary)
    {
        //cancel close by handling the event
        e.Handled = true;
    }
    deferral.Complete();
}