COMException -2147023728 when calling BackgroundTaskRegistration in MAUI WinUI project

ishebewhat 1

I downloaded the C#/WinRT example here for implementing background tasks and it runs successfully, but it's a WPF app. Attempting to do the same in a single or multi-project MAUI app results in COMException -2147023728 when calling BackgroundTaskRegistration. In fact, 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. No other modifications. Just the new project and this line of code. I'm using VS 2022 on Windows 10 build 19045.5371.

Leon Lu (Shanghai Wicresoft Co,.Ltd.) 78,916 Reputation points Microsoft Vendor

2025-01-20T06:23:06.3033333+00:00

it throws this exception.

Can you share the detailed exception?

do the same in a single or multi-project MAUI app results in COMException -2147023728 when calling BackgroundTaskRegistration

Did you add var registeredTasks = BackgroundTaskRegistration.AllTasks; in the MainPage's constructor?

Did you add BgTaskComponent in your project, then rebuild it, generate dll, then registering the background task(add Extensions) with the package manifest?

What is your .NET version?

Please edit your Question to include specific steps to reproduce this problem.
ishebewhat 1 Reputation point

2025-01-20T07:38:00.3066667+00:00

Well it's a MAUI project, and I called BackgroundTaskRegistration.AllTasks.Count in the WinUI App constructor and also tried in the shell using conditional compilation. I've followed the steps for authoring a C#/WinRT component that generates a .winmd component, and I can't get past the COMException when simply getting the AllTasks collection during runtime. It does generate the .winmd component. The problem is most easily reproduced by simply creating a new MAUI project, and adding that one line of code to the WinUI App constructor. Targeting .NET 9.
ishebewhat 1 Reputation point

2025-01-21T08:40:51.1933333+00:00

Since you mentioned the .NET version, I decided to try with a new .NET 8 project. It does work. But not with .NET 9. Creating the new project for .NET 8, then selecting .NET 9 for Windows prompts to install the Android SDKs when building.

1 answer

Leon Lu (Shanghai Wicresoft Co,.Ltd.) 78,916 Reputation points Microsoft Vendor

2025-01-21T08:51:08.0633333+00:00

Hello,

Since you mentioned the .NET version, I decided to try with a new .NET 8 project. It does work.

Thanks for your update, you can use .NET 8.

But not with .NET 9.

Q&A is not a bug reporting site. Please report this issue in the MAUI GitHub repo.

Best Regards,

Leon Lu

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ishebewhat 1 Reputation point

2025-01-25T01:16:43.9433333+00:00

Thanks. I wasn't sure it was a bug. Since you seem to be confirming so, I'll report as advised.
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COMException -2147023728 when calling BackgroundTaskRegistration in MAUI WinUI project

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