dotnet-system-commandline
dotnet-system-commandline
System.CommandLine 2.0 stable API for building .NET CLI applications. Covers RootCommand, Command, Option<T>, Argument<T>, SetAction for handler binding, ParseResult-based value access, custom type parsing, validation, tab completion, and testing with TextWriter capture.
Version assumptions: .NET 8.0+ baseline. System.CommandLine 2.0.0+ (stable NuGet package, GA since November 2025). All examples target the 2.0.0 GA API surface.
Breaking change note: System.CommandLine 2.0.0 GA differs significantly from the pre-release beta4 API. Key changes: SetHandler replaced by SetAction, ICommandHandler removed in favor of SynchronousCommandLineAction/AsynchronousCommandLineAction, InvocationContext removed (ParseResult passed directly), CommandLineBuilder and AddMiddleware removed, IConsole removed in favor of TextWriter properties, and the System.CommandLine.Hosting/System.CommandLine.NamingConventionBinder packages discontinued. Do not use beta-era patterns.
Out of scope: CLI application architecture patterns (layered command/handler/service design, configuration precedence, exit codes, stdin/stdout/stderr) -- see [skill:dotnet-cli-architecture]. Native AOT compilation -- see [skill:dotnet-native-aot]. CLI distribution strategy -- see [skill:dotnet-cli-distribution]. General CI/CD patterns -- see [skill:dotnet-gha-patterns] and [skill:dotnet-ado-patterns]. DI container mechanics -- see [skill:dotnet-csharp-dependency-injection]. General coding standards -- see [skill:dotnet-csharp-coding-standards].
Cross-references: [skill:dotnet-cli-architecture] for CLI design patterns, [skill:dotnet-native-aot] for AOT publishing CLI tools, [skill:dotnet-csharp-dependency-injection] for DI fundamentals, [skill:dotnet-csharp-configuration] for configuration integration, [skill:dotnet-csharp-coding-standards] for naming and style conventions.
Package Reference
<ItemGroup>
<PackageReference Include="System.CommandLine" Version="2.0.*" />
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