#csproj

How to split reusable code out of a game into an s&box Library package, and how to consume one from a game, without silently losing content, binding the wrong types, or shipping divergent assets.

s&box regenerates .csproj from the editor and gitignores them, so a fresh git worktree's Code/ and Editor/ folders have no project file and dotnet build fails MSB1009. Copy the csproj in, or, at a different depth, author one with absolute paths.

Compiling an s&box game assembly outside the editor needs the exact csproj shape the editor generates, and even a perfectly green offline build cannot surface whitelist violations. The SB1000 analyzer runs only in the editor compile pass, so code can build with 0 errors and 0 warnings offline and still be rejected in-editor. Build the editor-generated Code/<project>.csproj directly and confirm against the editor compile_status, never the offline build alone.

An s&box game csproj project-references the engine's Base Library csproj inside the Steam install. A first build or a rebuild writes generated intermediates into the engine tree even with an absolute OutputPath, and duplicate attribute files under the base addon then stop the engine booting. BaseIntermediateOutputPath is not the fix, it is a second trap. Clear the base addon's obj and .build folders to recover.

A fresh git worktree of an s&box project cannot dotnet build, because the editor generates Code/<project>.csproj and gitignores it, and the csproj references the Steam engine DLLs by relative paths tied to the main tree's directory depth. A naive copy fails with MSB3245 when the worktree nests one level deeper. The durable fix rewrites the csproj with absolute engine paths and redirects OutputPath into an isolated folder. That second half matters everywhere: the default OutputPath is the shared .vs/output/ folder with no project segment, so any CLI build on the machine writes into the same directory. A sibling build there empties a running editor's TypeLibrary, and every game component reads as MissingComponent while compile_status still reports Success. Build headless with the editor closed and output redirected, or pass -p:OutputPath to keep the build out of the shared directory.

A git worktree at a different directory depth than the main checkout breaks the generated csproj's relative references to the sbox install: dotnet build fails with missing-assembly errors.

A consumer game plus a vendored library can be compile-gated fully offline using two scratch csprojs against the editor install's prebuilt base library DLL.