C_SHARP_SKILLS/.ai/skills/02-csharp-language-fundamentals.md

Skill 02 - C# Language Fundamentals

Core Concepts

C# code is made of keywords, identifiers, literals, operators, expressions, statements, blocks, members, types, namespaces, and assemblies.

Naming Rules

• Use PascalCase for public types, methods, properties, events, and constants.
• Use camelCase for local variables and parameters.
• Use _camelCase for private fields when that is the project convention.
• Name things by meaning, not by type suffix, except accepted suffixes like Async, Options, Exception, Attribute, and Controller.

Variables and Constants

• Use var when the right side makes the type obvious.
• Use explicit types when they improve clarity or prevent accidental narrowing.
• Use const only for compile-time constants that will not change.
• Use readonly fields for values set during construction.
• Prefer immutable data where practical.

Strings

• Use string interpolation for readable formatting.
• Use StringBuilder for repeated string mutation in loops.
• Be explicit about culture for user-facing versus machine-readable formatting.
• Use ordinal comparisons for identifiers, keys, codes, and protocol values.
• Use culture-aware comparisons only for human language sorting/searching.

Console and Script-Like Code

• Top-level statements are fine for small apps, samples, and tools.
• Move logic into functions or classes once behavior needs tests.
• Keep Program.cs thin in production apps.

Style Rules

• Prefer clarity over language cleverness.
• Avoid unnecessary dynamic; use it only for genuinely dynamic data boundaries.
• Prefer pattern matching when it makes type and shape checks clearer.
• Use nameof(...) instead of string literals for member names.