including-generated-files

Add the generated .cs files to the Compile item group inside a target hooked with BeforeTargets="CoreCompile;BeforeCompile". This timing ensures the files exist before the compiler runs, since evaluation-phase globs cannot see files created during execution.

MSBuild expands globs during the evaluation phase, before any target runs, so files created during the build are never captured. Move the item declaration inside the generating target and add the files explicitly to the Compile item group.

Add every generated file to the FileWrites item group inside your generating target. The Clean target uses FileWrites to know which files to delete, so unregistered generated files accumulate as stale artifacts across builds.

Use CoreCompile;BeforeCompile for generated source files added to Compile, BeforeBuild for non-code files added to None or Content, and AssignTargetPaths as a fallback when BeforeBuild runs too early for item transformation.

No, always use $(IntermediateOutputPath) as the base directory for generated files. The intermediate output path can be redirected in shared output or CI configurations, so hardcoding obj\ breaks those builds.

No, Roslyn source generators already integrate with the compiler pipeline, and T4 design-time generation runs inside Visual Studio. This guidance targets custom MSBuild targets and tasks that produce files during build execution.