FileOpenPicker, FileSavePicker, and FolderPicker break in WinUI3 Desktop

[eleanorleffler]

Describe the bug

The FileOpenPicker, FileSavePicker, and FolderPicker in the WinUI3 Desktop sample solution break and close the application.

Steps to reproduce the bug

1. Clone the WinUI3 Problems FilePicker repository.

2. Go to the FilePickerWinUI folder.

3. Open the FilePickerWinUI solution in Visual Studio 2019 Preview.

4. Build and run with Debug x64.

5. Test each button

   A. FileOpenPicker

    1. Click the FileOpenPicker button.
    2. Select one or more files.
    3. Click [Open].
    4. The application will immediately close. 
   

   B. FileSavePicker

    1. Click the FileSavePicker button.
    2. The application should crash with an error. See Screenshot#1
   

   C. FolderPicker

    1. Click the FolderPicker button.
    2. Select one folder.
    3. Click [Select Folder].
    4. The application will immediately close.
   

Expected behavior

We expect the application to display the path of the selected file(s) or folder.

We expect the FileOpenPicker, FileSavePicker, and FolderPicker to allow the user to select files or a folder.

Screenshots

Screenshot#1 - Current Behavior (Error Message)

Screenshot#2 - Application Appearance

Version Info

NuGet package version:
[Microsoft.VCRTForwarders.140 1.0.6]
[Microsoft.WinUI 3.0.0-preview1.200515.3]

Targeting:
Target: Universal Windows
Target version: Windows 10, version 1809 (10.0; Build 17763)
Min version: Windows 10, version 1809 (10.0; Build 17763)

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
November 2019 Update (18363)
May 2019 Update (18362)
October 2018 Update (17763)	Yes
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Mobile
Xbox
Surface Hub
IoT

Additional context

We copied the related C# code from the microsoft/WinUI-3-Demos.

You will see this in App.xaml.cs and MainWindow.xaml.cs.

If we set the Debug -> Debugger Type -> Application proccess to Native Only, then the FolderPicker will work without crashing. However, the other two buttons will still not work.

[StephenLPeters]

@stevenbrix and @Scottj1s, @llongley thinks this is a CSWinrt issue. FYI.

[MikeHillberg]

I can't tell from the documentation, it could be that these pickers don't work in a Desktop (hwnd rather than CoreWindow) app.

[azchohfi]

It works if no debugger is attached, or if the Native Only debugger is attached. This seems like a tooling issue, or a Dot Net Core runtime issue. I believe these pickers worked fine on Xaml Islands.

[TheMrJukes]

I can't get any pickers to work at all in a Desktop (HWND) Win32 app using C++/WinRT.

necore\shell\lib\calleridentity\callerwindow_twinapi.cpp(116)\twinui.appcore.dll!00007FF8D3EC0BDC: (caller: 00007FF8D3E91E10) ReturnHr(1) tid(cd18) 80040155 Interface not registered
CallContext:[\PickSingleFileAsync\SingleStorageItemOperation]
Exception thrown at 0x00007FF905DD226C (KernelBase.dll) in App2.exe: WinRT originate error - 0x80070578 : 'Invalid window handle.'.
Exception thrown at 0x00007FF905DD226C in App2.exe: Microsoft C++ exception: winrt::hresult_error at memory location 0x000000305EF8CEE8.

winrt::fire_and_forget MainWindow::ShowPicker()
{
FileOpenPicker open;
open.SuggestedStartLocation(PickerLocationId::DocumentsLibrary);
open.FileTypeFilter().Append(L".txt");
auto file = co_await open.PickSingleFileAsync();
if (file)
{
}
}

EDIT:
I was pointed to a solution:
https://github.com/microsoft/WinUI-3-Demos/blob/0bc934a6716235a7f55e3f2a90f4dbb045a0697d/DemoBuildCpp/DemoBuildCpp/DemoBuildCpp/MainWindow.cpp#L140-L162

[jevansaks]

Since WinUI3 allows multiple windows on the same thread, the pickers can no longer assume there's just one and use it as the owner. You will need to use the IInitializeWithWindow interface to give the hint. Looks like the documentation has been updated to give some clues about this now:

FileOpenPicker and IInitializeWithWindow.