Fix for Page OnAppearing triggered twice when navigating via ShellItem change with PresentationMode set to Modal

[SyedAbdulAzeemSF4852]

Note

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It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!

Issue Details

• When navigating to a new ShellItem using a route like //SomeRoute/SomePage, and SomePage specifies Shell.PresentationMode="Modal", the page’s OnAppearing event is called twice.

Root Cause

• During Shell navigation between different ShellItems (e.g., //tab1 to //tab2/modal), modal pages receive duplicate lifecycle events because the old ShellSection calls SendDisappearing() on the modal page during its cleanup, but the modal page now belongs to the new ShellSection, which also manages its lifecycle events.

Description of Change

• Added an IsVisibleSection check in PresentedPageDisappearingmethod to ensure lifecycle events are only sent by the active ShellSection. This prevents duplicate events on modal pages during ShellItem transitions by blocking non-visible (previous) ShellSections from managing pages they no longer own.

Issues Fixed

Fixes #31584

Validated the behaviour in the following platforms

• Windows
• Android
• iOS
• Mac

Output

Platform	Before	After
iOS	iOS_Before.mov	iOS_After.mov
Android	Android_Before.mov	Android_After.mov

[dotnet-policy-service]

Hey there @@SyedAbdulAzeemSF4852! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed.