C# Engineering Fundamentals

A production-focused reference for C# language semantics, runtime behavior, API design, performance, and enterprise application development.

This repository is not organized as a syntax tutorial. Each module is an engineering dossier containing theory, memory and performance analysis, production notes, failure patterns, review guidance, senior interview questions, and compileable backend examples.

Table of Contents

• Engineering Model
• Engineering Quality
• Module Index
• Documentation Standard
• Runnable Scenarios
• Build and Validate
• Repository Structure
• Contribution Standard

Engineering Model

flowchart LR
    Semantics["Language semantics"] --> Contracts["API contracts"]
    Contracts --> Runtime["Memory and runtime"]
    Runtime --> Performance["Measured performance"]
    Performance --> Operations["Production behavior"]
    Operations --> Review["Review and interview reasoning"]

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Engineering Quality

Repository quality is enforced through small, reviewable changes and automated verification:

• Continuous integration: every push to main or a feature branch and every pull request to main restores and builds the solution in Release mode.
• Strict compilation: CI treats compiler warnings as errors to prevent warning debt from entering the stable branch.
• Documentation integrity: Markdown links are checked automatically when documentation changes.
• Reproducible tooling: workflows install the .NET 10 SDK explicitly instead of relying on the runner's preinstalled SDKs.
• Testing policy: no automated test project exists yet; when one is introduced, its test job should become a required pull-request check.

Module Index

Module	Engineering area	Code examples
01	Variables and State	4
02	Data Types and Representation	5
03	Type Conversion and Boundary Parsing	5
04	Operators and Expression Semantics	8
05	Strings, Text, Culture, and Encoding	8
06	Arrays, Spans, and Contiguous Memory	8
07	Methods, Contracts, and API Shape	4
08	Control Flow and Business Decisions	4
09	Exceptions, Resilience, and Failure Semantics	4
10	Namespaces, Assemblies, and Dependency Boundaries	4

Documentation Standard

Every module contains:

• README.md — decision-oriented overview and navigation;
• Theory.md — language and runtime semantics;
• BestPractices.md — implementation and review checklist;
• CommonMistakes.md — production failure patterns;
• InterviewQuestions.md — 10 senior-level questions with answers;
• ProductionNotes.md — enterprise use, memory, performance, and Microsoft-aligned recommendations;
• compileable .cs examples using orders, payments, users, claims, services, and infrastructure boundaries.

Runnable Scenarios

The application includes executable order processing, payment validation, and notification dispatch examples.

dotnet run --project src/CSharpFundamentals/CSharpFundamentals/CSharpFundamentals.csproj
dotnet run --project src/CSharpFundamentals/CSharpFundamentals/CSharpFundamentals.csproj -- payment

See the execution guide.

Build and Validate

Requires the .NET 10 SDK.

dotnet restore src/CSharpFundamentals/CSharpFundamentals.slnx
dotnet build src/CSharpFundamentals/CSharpFundamentals.slnx --configuration Release

Repository Structure

csharp-fundamentals/
├── assets/
├── examples/
└── src/CSharpFundamentals/CSharpFundamentals/
    ├── Examples/                  # Executable cross-topic scenarios
    └── Modules/
        ├── 01-Variables/
        ├── 02-DataTypes/
        ├── 03-TypeConversion/
        ├── 04-Operators/
        ├── 05-Strings/
        ├── 06-Arrays/
        ├── 07-Methods/
        ├── 08-ControlFlow/
        ├── 09-ExceptionHandling/
        └── 10-Namespaces/

Contribution Standard

• Explain the production decision, not only the syntax.
• Keep examples compileable and domain-oriented.
• Include memory, performance, failure, and testing implications.
• Prefer primary Microsoft references.
• Avoid toy models, empty placeholders, and unexplained snippets.

License

Distributed under the MIT License.

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C# semantics connected to production engineering decisions.