[Packaged App]co_await does't return to ui thread. when the call PickSingleFolderAsync is completed

[shelllet]

Describe the bug

Internal bug https://task.ms/37013204

windowsappsdk preivew-3:
StorageFolder folder = co_await picker.PickSingleFolderAsync();

at this point

call DependencyObject::SetValue throw errors.

The application called an interface that was marshalled for a different thread
//

Steps to reproduce the bug

1. Create c++ package app by windowsappsdk.

2. Call FolderPicker to open select folder dialog on button clicked event.

3. then DependencyObject::SetValue

Expected behavior

before windowsappsdk preview-3

c++/winrt will restore to ui thread automatically.

why preview-3 change this ？

Screenshots

NuGet package version

1.0.0-preview3

Packaging type

Packaged (MSIX)

Windows version

Windows 11 (22000)

IDE

Visual Studio 2022

Additional context

to avoid me bebing wrong, I recreate an empty pacakged project and test .

unpackaged app:

[andrewleader]

@BenJKuhn @Scottj1s would this co_await issue be either of your areas of expertise? It sounds like in Preview 3 we possibly regressed the behavior of co_await in C++ apps and it doesn't return back to the UI thread anymore?

[andrewleader]

@BenJKuhn this looks like a dupe of https://microsoft.visualstudio.com/OS/_workitems/edit/37013204 which @MikeHillberg is assigned to. @MikeHillberg is this indeed a dupe of your co_await bug?

[BenJKuhn]

This was fixed some time ago (in 1.0, I believe), but the public issue never got closed out. Just cleaning up books.