Error in VS Code's LanguageServerProjectSystem with Conditional Target Frameworks

[kristoffer-tungland]

Issue Type: Bug

• VS Code Version: Latest stable
• OS Version: Windows

Steps to Reproduce:

1. Create a multi-configuration project structure with conditional target frameworks:

   • Main project file that imports a common targets file
   • Common targets file that conditionally imports version-specific targets based on configuration
   • Version-specific targets files with different target frameworks (net48 vs net8.0-windows)

2. Open the project in VS Code with C# Dev Kit or C# extension enabled

3. Observe the error in Output panel: "The 'ResolvePackageAssets' task was not given a value for the required parameter 'TargetFramework'"

Expected Behavior

The language server should load the project successfully and provide IntelliSense based on the selected build configuration.

Actual Behavior

The language server fails to load the project with the error:

Error while loading c:\Users\...\RevitExtension3.csproj: The "ResolvePackageAssets" task was not given a value for the required parameter "TargetFramework".

Workarounds Attempted

1. Added Directory.Build.props with default TargetFramework value - only works for .NET Framework but not .NET Core targets
2. Modified targets files to be more explicit about target framework selection
3. Command-line builds work correctly (dotnet build -c "Debug 2025") but the language server still fails

Relevant Files

• Project structure:

  RevitExtension3.csproj
  RevitExtension3Command.cs
  Directory.Build.props
  targets/
    CommonRevit.targets
    Revit2024.targets (net48)  
    Revit2025.targets (net8.0-windows)
  

Extension Bisect Results

Issue is specific to the C# language server/C# Dev Kit when dealing with conditionally defined target frameworks.

Additional Information

• The issue only affects IDE tooling (IntelliSense, code navigation)
• Command-line builds work correctly
• Appears to be a limitation in how the language server resolves conditional imports and target frameworks

Repo with test files

https://github.com/kristoffer-tungland/RevitExtension3