Blazor dotnet publish error Microsoft.NET.Sdk.BlazorWebAssembly.ComputeBlazorPublishAssets.GroupExistingStaticWebAssets

[DjeeBay]

I have a Blazor project recently upgraded from .NET 3.1 to 6.0 that cannot be published anymore due to the following error when publishing :

System.ArgumentException: An item with the same key has already been added Microsoft.NET.Sdk.BlazorWebAssembly.ComputeBlazorPublishAssets.GroupExistingStaticWebAssets

The binlog shows that the problem comes from referenced assemblies (.dll) that I have in the Shared project. If I remove those assemblies the project can be published.

A simple repro can be done on a brand new Blazor wasm project, referencing a simple .dll that does nothing in the shared project. With .Net 6.0 publishing won't work, but with 5.0 it will.

Any chances that this will be fixed soon, or is there a workaround to manage to publish ?

[TanayParikh]

Hello @DjeeBay, thanks for reaching out. Can you confirm if you did a full project clean before attempting to publish in .NET 6? Please try deleting the bin & obj folders as well.

[ghost]

Hi @DjeeBay. We have added the "Needs: Author Feedback" label to this issue, which indicates that we have an open question for you before we can take further action. This issue will be closed automatically in 7 days if we do not hear back from you by then - please feel free to re-open it if you come back to this issue after that time.

[DjeeBay]

Hello @DjeeBay, thanks for reaching out. Can you confirm if you did a full project clean before attempting to publish in .NET 6? Please try deleting the bin & obj folders as well.

Hi @TanayParikh, yes I did and like I said I can reproduce on a brand new project to confirm this behavior with .NET 5.0 against .NET 6.0.

[MariovanZeist]

@DjeeBay I had a similar problem, it turned out there were 2 projects with the same content. Both projects had a "package.json" with their Build action set to content. setting the Build action to none fixed it for me.

[DjeeBay]

@MariovanZeist yes I saw that in some projects there are some identical filename issues (#38186, #37610, #35633) but not in my case. The build action didn't change anything either.

Just try to create a new Blazor wasm project, then create elsewhere a new standard 2.0 project, then add a reference of the standard 2.0 .dll into the Blazor Shared project.

You won't be able to publish with .NET 6.0, but with .NET 5.0 you will. (don't forget to use your dll, in WeatherForecast.cs for instance)

[MariovanZeist]

@DjeeBay Could you create a minimal repro? using your instructions ended up working for me, so possibly I didn't understand your instructions exactly.

[DjeeBay]

@MariovanZeist here we go : https://github.com/DjeeBay/BlazorNET6WontPublish

The "HelloStandard.dll" referenced in the Shared project does nothing, it's just a new standard 2.0 project.

[MariovanZeist]

@DjeeBay Thank you for the repo. I am able to reproduce your problem. But I don't know a solution.

[TanayParikh]

Hello @DjeeBay, I believe this issue may have been resolved in the most recent patch .NET 6.0.1, which will be coming out today. Could you please give that a try once it's available.

[DjeeBay]

Hello @TanayParikh, it works as expected now with .NET 6.0.101.

Great job !

[TanayParikh]

Great to hear, thanks for checking!