# 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.