dotnet-file-based-apps

.NET 10 SDK file-based apps let you build, run, and publish C# applications from a single .cs file without creating a .csproj project file. The SDK auto-generates project configuration from #: directives embedded in the source file. This feature targets scripts, utilities, and small applications where traditional project scaffolding is unnecessary.

This is NOT file I/O. For FileStream, RandomAccess, FileSystemWatcher, and path handling, see [skill:dotnet-file-io].

Prerequisites: Requires .NET 10 SDK or later. Run [skill:dotnet-version-detection] to confirm SDK version.

Cross-references: [skill:dotnet-version-detection] for SDK version gating, [skill:dotnet-project-analysis] for project-based analysis (file-based apps have no .csproj), [skill:dotnet-scaffold-project] for csproj-based project scaffolding.

Directives Overview

File-based apps use #: directives to configure the build. Directives are SDK-level instructions, not C# syntax. They must appear at the top of the .cs file, before any C# code.

Four directive types are supported: