Weird issues in Visual Studio 2022: Solving the CS0534 error when solving the Json trimming problem

 TL/DR: Visual Studio 2022 is wrong, and your code is OK

Background: I'm having to switch from the awesome NewtonSoft JSON library over to some crappy System.Text.Json library (because VS thinks that breaking everyone to support Trimming is somehow ever OK). The sample code for that is wrong, but that's OK, it points to the right code.

Except that if you copy-paste the sample code, it fails:

The error, BTW, is CS5034: 'SourceGenerationContextErrorCS0534' does not implement inherited abstract member 'JsonSerializerContext.GetTypeInfo(Type)' and also '...does not implement inherited abstract member 'JsonSerializerContext.GeneratedSerializerOptions.get' and also 'CS7035: There is no argument given that corresponds to the required parameter 'options' of 'JsonSerializerContext(JsonSerializeroptions?)'.

Solution: just recompile. It turns out that every single thing about the error is wrong. The correct solution is to "recompile your code". That's because Visual Studio 2022 is focused on everything other than the day-to-day experience of programmers.

Weird issues in Visual Studio 2022 ┄ missing publish profiles with WinUI Blank App Packaged

 

TL/DR: Desktop .NET Core apps might be missing a Publish directory because it's in the .github ignore list. The files are actually all very similar and can be copy-pasted from another project.

Background: 

A part of the .NET Core is that projects are both "built" and "published". This has apparently been around for ages. The problem is that there's a terrible split in the tooling: some parts of the tooling consider "publishing" to be essential and won't work if you don't have some publishing files set up. But other parts of the tooling consider "publishing" to be dangerous and therefore should be excluded from GitHub.

Helpful links:

Format of the .gitignore file: git-scm.com

There is no findable documentation for pubxml files. A web search shows a bunch of information related to ASP.NET

Solution:

The solution has two parts: get new version of the missing pubxml files and add them to GitHub.

1. Get new pubxml files from a new WinUI Blank App (packaged) project that you create in a temporary directory. Copy the entire PublishProfiles directory (it has to be called that for the builds to work). The directory should have three pubxml files in it.

AFAICT, the files are always the same for each project.

2. Update your .GITIGNORE file to allow the PublishProfiles directory to be saved. Warning: not all pubxml files should be put into GitHub. Some pubxml files include secret information like passwords and connection strings.

Perhaps the safest change is to add this line:

# 2025-07-19: shipwreck software: WinUI Blank App (Packaged) requires the win-arm64.pubxml,
# win-x64.pubxml and win-x86.pubxml files for the Release mode compile to work
# BUT pubxml files can include secret information, so we should not just allow all
# pubxml files to be added to GitHub.
!win-*.pubxml

Error messages:

These error messages pop up when building a WinUI Blank App Packaged (2025-07-18)

Code Description Project File
NETSDK1198 A publish profile with the name 'win-x64.pubxml' was not found in the project. Set the PublishProfile property to a valid file name. WinUI_Blank_App_Packaged_2025_07_15 C:\Program Files\dotnet\sdk\9.0.302\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.Publish.targets
NETSDK1102 Optimizing assemblies for size is not supported for the selected publish configuration. Please ensure that you are publishing a self-contained app. WinUI_Blank_App_Packaged_2025_07_15 C:\Users\USER\.nuget\packages\microsoft.net.illink.tasks\8.0.18\build\Microsoft.NET.ILLink.targets

VS: Don't start your project names with letters!

 Weird issues in Visual Studio 2022 -- an ongoing saga

Ever get an error in a brand new project saying that "App.WinRTVtable.g.cs" is failing and that "global::WinRT is a namespace?Tearing your hair out because what in the world could you have done to make this fail?

It turns out it's your project name. When you make a WinUI Blank App (Packaged) in Visual Studio 2022, and the project name starts with a number, it makes a broken project.

Links:

GitHub project demonstrating the problem: link.

Existing bug: Build Errors when assemblyname starts with a number · Issue #1880 · microsoft/CsWinRT

The bug claims it will be fixed soon in "2.3.0", whatever that is.

Here's the dump from the Output window for building.

1>------ Build started: Project: 2_WinUI_Blank_App_Packaged_2025_07_15, Configuration: Debug x64 ------

1>C:\temp\2025\testrepos\VSBugReportSolution\2_WinUI_Blank_App_Packaged_2025_07_15\obj\x64\Debug\net8.0-windows10.0.19041.0\win-x64\intermediatexaml\WinRT.SourceGenerator\Generator.WinRTAotSourceGenerator\_2_WinUI_Blank_App_Packaged_2025_07_15.App.WinRTVtable.g.cs(4,40,4,53): error CS0118: 'global::WinRT' is a namespace but is used like a type

1>C:\temp\2025\testrepos\VSBugReportSolution\2_WinUI_Blank_App_Packaged_2025_07_15\obj\x64\Debug\net8.0-windows10.0.19041.0\win-x64\intermediatexaml\WinRT.SourceGenerator\Generator.WinRTAotSourceGenerator\_2_WinUI_Blank_App_Packaged_2025_07_15.App.WinRTVtable.g.cs(4,56,4,104): error CS0103: The name 'WinUI_Blank_App_Packaged_2025_07_15VtableClasses' does not exist in the current context

1>C:\temp\2025\testrepos\VSBugReportSolution\2_WinUI_Blank_App_Packaged_2025_07_15\obj\x64\Debug\net8.0-windows10.0.19041.0\win-x64\intermediatexaml\WinRT.SourceGenerator\Generator.WinRTAotSourceGenerator\_2_WinUI_Blank_App_Packaged_2025_07_15.App.WinRTVtable.g.cs(4,2,4,164): error CS1729: 'WinRTExposedTypeAttribute' does not contain a constructor that takes 3 arguments

1>Done building project "2_WinUI_Blank_App_Packaged_2025_07_15.csproj" -- FAILED.