form does not support code parsing or generation becausew it is not contained within a project that supports this code

Question

1>------ Rebuild started: Project: PayDay, Configuration: Debug|AnyCPU ------

1>C:\Program Files\dotnet\sdk\9.0.313\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.EolTargetFrameworks.targets(32,5): warning NETSDK1138: The target framework 'net6.0-windows' is out of support and will not receive security updates in the future. Please refer to https://aka.ms/dotnet-core-support for more information about the support policy.

1>C:\Program Files\dotnet\sdk\9.0.313\Sdks\Microsoft.NET.Sdk\targets\Microsoft.PackageDependencyResolution.targets(266,5): error MSB4018: The "ResolvePackageAssets" task failed unexpectedly.

C:\Program Files\dotnet\sdk\9.0.313\Sdks\Microsoft.NET.Sdk\targets\Microsoft.PackageDependencyResolution.targets(266,5): error MSB4018: NuGet.Packaging.Core.PackagingException: Unable to find fallback package folder 'C:\Program Files (x86)\Microsoft Visual Studio\Shared\NuGetPackages'.

C:\Program Files\dotnet\sdk\9.0.313\Sdks\Microsoft.NET.Sdk\targets\Microsoft.PackageDependencyResolution.targets(266,5): error MSB4018: at NuGet.Packaging.FallbackPackagePathResolver..ctor(String userPackageFolder, IEnumerable`1 fallbackPackageFolders)

C:\Program Files\dotnet\sdk\9.0.313\Sdks\Microsoft.NET.Sdk\targets\Microsoft.PackageDependencyResolution.targets(266,5): error MSB4018: at Microsoft.NET.Build.Tasks.NuGetPackageResolver.CreateResolver(IEnumerable`1 packageFolders)

Answer 1

The build log shows two separate issues:

1. NETSDK1138: The target framework 'net6.0-windows' is out of support
2. MSB4018: ResolvePackageAssets failed because it cannot find the fallback NuGet package folder

Address them in this order.

1. Fix the out‑of‑support target framework

net6.0-windows is out of support. To bring the project back into support, edit the project file (.csproj or .vbproj) and change the target framework to a supported one, for example:

<PropertyGroup>
  <TargetFramework>net8.0-windows</TargetFramework>
</PropertyGroup>

If changing the target framework is not possible right now and the goal is only to get rid of the warning, add this property instead:

<PropertyGroup>
  <CheckEolTargetFramework>false</CheckEolTargetFramework>
</PropertyGroup>

This suppresses NETSDK1138 while still targeting the old framework.

2. Fix the NuGet fallback package folder error

The error

Unable to find fallback package folder 'C:\Program Files (x86)\Microsoft Visual Studio\Shared\NuGetPackages'

means the SDK is configured to use that path as a fallback package folder, but the folder does not exist on disk.

Use one of these approaches:

• Create the folder manually at C:\Program Files (x86)\Microsoft Visual Studio\Shared\NuGetPackages and rebuild, or
• Remove/adjust the fallback folder configuration (for example, in NuGet.Config or MSBuild properties) so it no longer points to that path.

Once the fallback folder path is valid (or removed) and the project targets a supported framework (or has CheckEolTargetFramework disabled), the ResolvePackageAssets task should complete and the project should build.

The designer message

form does not support code parsing or generation because it is not contained within a project that supports this code

is typically a consequence of the project not loading/building correctly. After fixing the target framework and NuGet configuration so the project builds successfully, close and reopen the solution; the Windows Forms designer should then be able to parse and generate code again.

---

References:

• NETSDK1138: The target framework is out of support