dotnet.generateAssets persists C# Dev Kit temporary solution paths in build and publish tasks #9748

Type: Bug

Summary

dotnet.generateAssets can persist C# Dev Kit’s temporary solution path in generated tasks instead of the application’s .csproj. This produces machine-specific configuration and, when the workspace and temporary solution are on different Windows drives, an invalid path.

This affects Container Tools’ Add Docker Files to Workspace command, which delegates .NET asset generation to the C# extension. Tracked downstream in microsoft/vscode-containers#605.

Steps to reproduce

1. Install the C# and C# Dev Kit extensions.
2. Create an ASP.NET Core project without a solution file on a drive different from VS Code’s user-data directory:

   dotnet new mvc -o D:\Sandbox\ExampleApp

3. Open that folder in VS Code and allow Dev Kit to load it in workspace mode.
4. Run Containers: Add Docker Files to Workspace, selecting ASP.NET Core and Linux.
5. Inspect the generated .vscode/tasks.json and run the build task.

Container Tools invokes:

vscode.commands.executeCommand(
    'dotnet.generateAssets',
    undefined,
    { skipPrompt: true }
);

Reproduced with:

• Container Tools 2.5.0
• C# 2.140.9
• C# Dev Kit 3.20.207
• .NET SDK 10.0.400
• Windows, with the project on D: and VS Code user data on C:

Actual behavior

The generated build, publish, and watch tasks reference a path shaped like:

./${workspaceFolder}/c:/Users/<user>/AppData/Roaming/Code/User/workspaceStorage/<id>/ms-dotnettools.csdevkit/ExampleApp.sln

The build fails with:

MSBUILD : error MSB1009: Project file does not exist.

The original temporary solution does exist on C:. The generated argument is malformed. Building the actual .csproj succeeds.

Even without the cross-drive failure, persisting a solution under VS Code’s workspace storage makes the configuration dependent on the generating user’s environment.

Expected behavior

Persist the selected project’s workspace-relative path in build, publish, and watch tasks, regardless of whether Dev Kit is installed:

${workspaceFolder}/ExampleApp.csproj

Checked-in configuration should work for teammates using the C# extension and .NET SDK without requiring Dev Kit or its generated temporary solution.

Investigation

In src/shared/assets.ts:

• getBuildProjectPath() prefers any nonempty solutionPath over projectPath.
• getBuildPath() unconditionally joins ${workspaceFolder} with path.relative(workspace, target). Across Windows drives, the latter returns an absolute path, making the join invalid.

Solution preference was introduced by commit 7fb0321. Dev Kit’s solution-free workspace behavior exposes this by creating solutions outside the workspace.

#9704 already changes watch to use the project path. Build and publish still prefer the solution.

Suggested resolution

Prefer project paths for newly generated persisted tasks, leaving existing user-authored tasks unchanged.

If solution-based build/publish defaults must be retained, please expose a supported dotnet.generateAssets option to request project-based tasks. Currently, selectedIndex selects a project but does not override solution preference, and skipPrompt only controls the Dev Kit recommendation dialog.

Such an option would let Container Tools request portable configuration without duplicating C# asset generation or post-processing tasks.json and launch.json.

Extension version: 2.140.9
VS Code version: Code 1.137.0 (645f29cc3176500b4b5762ba887cf2a7f0ffdf2c, 2026-09-08T13:43:59-07:00)
OS version: Windows_NT x64 10.0.26200
Modes:

Logs

C# log

2026-09-10 12:01:59.170 [info] Locating .NET runtime version 10.0.5
2026-09-10 12:01:59.455 [info] Dotnet path: C:\Program Files\dotnet\dotnet.exe
2026-09-10 12:01:59.455 [info] Activating C# + C# Dev Kit...
2026-09-10 12:02:00.047 [info] info: Program[0]
2026-09-10 12:02:00.047 [info]       Server started with process ID 9236
2026-09-10 12:02:00.875 [info] [Program] Language server initialized
2026-09-10 12:02:00.877 [info] [Program] Monitoring client process 9804 for exit
2026-09-10 12:02:01.531 [info] [initialized] [Microsoft.CodeAnalysis.LanguageServer.FileBasedPrograms.FileBasedProgramsEntryPointDiscovery] Finished discovery in 'd:\Sandbox\ContainersIssue605-55ffe9f3' in 9 milliseconds
2026-09-10 12:02:04.881 [info] [serviceBroker/connect] [WorkspaceProjectFactoryService] Project D:\Sandbox\ContainersIssue605-55ffe9f3\ContainersIssue605.csproj loaded by C# Dev Kit

C# LSP Trace Logs log

Environment Information

VSCode version: 1.137.0
C# Extension: 2.140.9
Using OmniSharp: false