Fixes #3673 and resolves issues with some samples not working correctly

[michael-hawker]

Fixes #3673

Forgot to check some scenarios in the original update to #3648 and broke scenarios of pages with code-behind. This PR resolves that and forward-fixes all sample types (XAML only, code-behind, code-behind + XamlRoot).

PR Type

What kind of change does this PR introduce?

• Bugfix

• Refactoring (no functional changes, no api changes)

What is the current behavior?

If a sample page didn't have a XamlRoot defined in it's page it was getting obliterated in the UpdateXamlRender call.

What is the new behavior?

Clearly defined what a SamplePage was (to be the backing instance of a sample (if one)). Then used that to instead overwrite it's content as intended if there is no XamlRoot instead of the entire page itself.

i.e. the bug was that we were replacing the entire page with the rendered XAML and therefore no longer held an instance to call IXamlRenderListener on. This fix now checks for that condition and only updates the inner page content vs. our entire hosted content within the Sample.

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Pull Request has been submitted to the documentation repository instructions. Link:
• Sample in sample app has been added / updated (for bug fixes / features)
  • Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• New major technical changes in the toolkit have or will be added to the Wiki e.g. build changes, source generators, testing infrastructure, sample creation changes, etc...
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Header has been added to all new source files (run build/UpdateHeaders.bat)
• Contains NO breaking changes

FYI @RosarioPulella, @Kyaa-dost

[ghost]

Thanks michael-hawker for opening a Pull Request! The reviewers will test the PR and highlight if there is any conflict or changes required. If the PR is approved we will proceed to merge the pull request 🙌

[michael-hawker]

Once we validate and merge this to the main branch we can update the dev branches as well. FYI @Sergio0694

[Rosuavio]

Seems to have fixed things to me,

[michael-hawker]

@Kyaa-dost want to test out a smattering of some different samples and let us know how it goes? The 'Trigger' samples under helpers use the new XAML only setup, and then anything with buttons on the bottom is using code-behind, and anything with other content around the sample is using code-behind + xamlroot.

[Kyaa-dost]

Thanks, @michael-hawker!! Tested out lots of lots of samples and are performing as expected 🚀

[ghost]

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