[windows] Fixed Rapid change of selected tab results in crash.

[praveenkumarkarunanithi]

Root Cause

On Windows, TabbedPage uses WinUI Frame navigation to display each tab’s content. Each tab’s platform view (native UI element) is hosted inside a WinUI Page through a ContentPresenter.
During rapid tab switching, the platform view is reassigned to a new WinUI Page while still attached to the previous one. WinUI does not allow a UI element to exist in two visual trees simultaneously, which causes the crash.

Description of Change

Added a _displayedPage tracking field to maintain the correct displayed MAUI Page during navigation, allowing NavigateToPage to skip early if the requested page is already displayed and avoid redundant navigation. The method also now clears the previous WinUI Page’s ContentPresenter to explicitly detach the platform view and prevent the “element already has a parent” WinUI error. In UpdateCurrentPageContent, a skip guard avoids reassigning content that is already set, while _displayedPage is updated only after successful content assignment. Finally, OnHandlerDisconnected resets _displayedPage to null to ensure proper cleanup and prevent stale references.

Issues Fixed

Fixes #32824

Tested the behaviour in the following platforms

• Android
• Windows
• iOS
• Mac

Output Video

Before Issue Fix	After Issue Fix

[Copilot]

Pull request overview

This pull request fixes a Windows-specific crash in TabbedPage when rapidly switching between tabs. The crash occurred because during rapid tab switches, platform views were being reassigned to new WinUI Pages while still attached to previous ones, violating WinUI's constraint that a UI element cannot exist in multiple visual trees simultaneously.

Key Changes

• Added _displayedPage tracking field to prevent redundant navigation and track which MAUI Page is currently displayed
• Added content detachment logic in NavigateToPage to explicitly clear the previous WinUI Page's ContentPresenter before navigation
• Added guard condition in UpdateCurrentPageContent to skip updates when the requested page is already displayed

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/Controls/src/Core/TabbedPage/TabbedPage.Windows.cs	Implements the fix by adding _displayedPage field, clearing old content before navigation, and adding guard conditions to prevent redundant updates
src/Controls/tests/DeviceTests/Elements/TabbedPage/TabbedPageTests.Windows.cs	Adds regression test to verify old ContentPresenter content is cleared during tab switches

[Copilot]

The code uses BindingFlags but the required using directive for System.Reflection is missing from the file. This will cause a compilation error. Add 'using System.Reflection;' to the top of the file with the other using statements.