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name: project-setup description: "Create or reorganize .NET solutions with clean project boundaries, repeatable SDK settings, and a maintainable baseline for libraries, apps, tests, CI, and local development. USE FOR: creating a new .NET solution or restructuring an existing one; setting up Directory.Build.props, shared package management, or repo-wide defaults; defining project. DO NOT USE FOR: unrelated stacks; generic tasks that do not need this specific guidance. INVOKES: inspect the repository context, edit targeted files, and run relevant build, test, lint, or validation commands when changes are made." compatibility: "Best for new repositories or structural refactors of existing .NET solutions."

.NET Project Setup

Trigger On

• creating a new .NET solution or restructuring an existing one
• setting up Directory.Build.props, shared package management, or repo-wide defaults
• defining project layout for apps, libraries, and test projects

Workflow

1. Start from the app model and deployment target, then choose the smallest correct SDK and target framework set.
2. Use solution folders and project names that reflect bounded contexts or product areas, not temporary implementation details.
3. Centralize shared build settings, analyzer rules, nullable context, and package versions where it reduces duplication without hiding important differences.
4. Create test projects and CI hooks early so new projects do not drift into unverified templates.
5. Prefer project references and composition over circular dependencies or utility dumping grounds.
6. Document the local build, test, and run path in repo docs or AGENTS.md when the workflow is not obvious.

Current Upstream Notes

• The August 2026 "Build apps with .NET" Learn overview reinforces app-model-first setup: console, web, worker, desktop, mobile, cloud, and AI entry points should drive SDK/template choice.
• .NET SDK 10.0.400 is the current 10.0.4xx feature band. It expands file-based app support, adds Microsoft.Testing.Platform --project and --solution selection to dotnet test, accepts @ as the dotnet new option separator, and fixes hardlink and incremental-build paths. Keep global.json, workloads, and CI images explicit for the selected feature band.

Deliver

• a coherent solution structure
• shared build defaults that are easy to reason about
• starter quality and testing hooks for future work

Validate

• projects have explicit responsibility boundaries
• shared MSBuild settings do not accidentally override platform-specific needs
• a new contributor can build and test the repo without guessing

References

• patterns.md: solution layout conventions, Directory.Build.props, Directory.Build.targets, Central Package Management, global.json, nuget.config, analyzers, multi-targeting, and source link
• templates.md: dotnet new templates for console apps, class libraries, ASP.NET Core APIs, worker services, Blazor, test projects, .NET Aspire, and gRPC services