COMException -2147023728 when calling BackgroundTaskRegistration in MAUI WinUI project

[Mvk3aJKQh]

Description

I created both a brand new single and multi-app MAUI project, and added System.Diagnostics.Debug.WriteLine(Windows.ApplicationModel.Background.BackgroundTaskRegistration.AllTasks.Count); to the WinUI App constructor after InitializeComponent(); and it throws this exception. Works for .NET 8, but not for .NET 9. Creating the new project for .NET 8, then selecting .NET 9 for Windows prompts to install the Android SDKs when building.

Steps to Reproduce

1. Create a new .NET 9 MAUI project
2. Add System.Diagnostics.Debug.WriteLine(Windows.ApplicationModel.Background.BackgroundTaskRegistration.AllTasks.Count); to the WinUI App constructor after InitializeComponent();
3. Run

Link to public reproduction project repository

https://github.com/Mvk3aJKQh/COMException-2147023728

Version with bug

9.0.14 SR1.4

Is this a regression from previous behavior?

Yes, this used to work in .NET MAUI

Last version that worked well

.NET 8

Affected platforms

Windows

Affected platform versions

Windows 10 build 19045.5371

Did you find any workaround?

No response

Relevant log output

System.Runtime.InteropServices.COMException
  HResult=0x80070490
  Message=
  Source=WinRT.Runtime
  StackTrace:
   at WinRT.ExceptionHelpers.<ThrowExceptionForHR>g__Throw|38_0(Int32 hr)
   at WinRT.ExceptionHelpers.ThrowExceptionForHR(Int32 hr)
   at ABI.Windows.ApplicationModel.Background.IBackgroundTaskRegistrationStaticsMethods.get_AllTasks(IObjectReference _obj)
   at Windows.ApplicationModel.Background.BackgroundTaskRegistration.get_AllTasks()
   at Product.Platforms.Windows.App..ctor() in {ProjectPath}\Platforms\Windows\App.xaml.cs:line 11
   at Product.Platforms.Windows.Program.<>c.<Main>b__0_0(ApplicationInitializationCallbackParams p) in {OutputPath}\obj\Debug\net9.0-windows10.0.19041.0\win10-x64\Platforms\Windows\App.g.i.cs:line 29
   at ABI.Microsoft.UI.Xaml.ApplicationInitializationCallback.Do_Abi_Invoke(IntPtr thisPtr, IntPtr p)

[Mvk3aJKQh]

Added link to repository

[RoiChen001]

I can repro this issue at Windows platform on the latest 17.13 Preview 5(9.0.30 & 9.0.14), but the exception does not exist in 8.0.100.

[mattleibow]

Is this a packaged or unpackaged app?

Seems to be this: microsoft/WindowsAppSDK#4201

Even this: microsoft/CsWinRT#1518

[mattleibow]

@RoiChen001 are you able to use .net 8 and upgrade the Windows App SDK to the latest?

[mattleibow]

Does this happen on Windows 11 AND Windows 10?