build-perf-baseline

Measure three scenarios: cold build after deleting bin/obj folders, warm build after touching one source file, and no-op build with no changes. Use dotnet build with /bl to capture binary logs for each scenario and compare timings in a before/after table.

Start by baselining cold, warm, and no-op builds to find where time goes. Then apply targeted fixes: enable MSBuild Server, use /graph for static graph builds, trim redundant ProjectReferences, separate restore from build, and tune parallelism with -m.

A no-op build should take under 5 seconds for small repos and under 30 seconds for large repos, with all compilation targets reporting up-to-date. If it exceeds 30 seconds, incremental build is broken and Inputs/Outputs declarations need fixing.

Use /graph for large solutions with 20 or more projects and in CI, where static graph evaluation improves scheduling and parallelism. Avoid it for small solutions under 5 projects where graph evaluation overhead outweighs the benefits.

Full recompilation on warm builds usually means the project dependency chain forces downstream rebuilds. Trim redundant transitive ProjectReferences, use ReferenceOutputAssembly="false" for build-order-only dependencies, and check the binlog for the triggering project.

UseArtifactsOutput, introduced in .NET 8, redirects all build output into a single artifacts directory with unique paths per project and configuration. It eliminates bin/obj clashes, simplifies CI caching, and reduces .gitignore maintenance.