C# Code Style Guide

Overview

C# 코딩 표준 (POCU 기반, C# 9.0 기준)

Core Topics:

• 명명 규칙 (m접두어, b접두어, E/S접두어)
• 코드 작성 규칙
• 클래스 구조 순서
• C# 9.0 패턴

Language Note

이 문서는 한국어를 기본으로 작성되었으며, 코드 예제와 기술 용어는 영어를 사용합니다. 섹션 제목은 영어로 통일하고, 설명과 주석은 한국어로 작성합니다.

• 섹션 제목: 영어 (Naming Conventions, Code Writing Rules 등)
• 설명/주석: 한국어
• 코드 예제: 영어 (변수명, 클래스명, 코드 코멘트)
• 표(Table) 헤더: 영어, 내용은 영어 또는 한국어 혼용 가능

Naming Conventions

Quick Reference

Element	Convention	Example
Class	PascalCase	PlayerManager, OrderService
Struct	SPascalCase	SUserID, SPlayerData
Interface	IPascalCase	IDisposable, IOrderService
Enum	EPascalCase	EDirection, EOrderStatus
Method (public)	PascalCase (동사+명사)	GetAge(), ProcessOrder()
Method (private)	camelCase	getAge(), processOrder()
Property	PascalCase	Name, OrderID
Private Field	mPascalCase	mAge, mOrderRepository
Local Variable	camelCase	totalAmount, isValid
Parameter	camelCase	customerId, orderDate
Constant	ALL_CAPS	MAX_RETRY_COUNT, DEFAULT_TIMEOUT
Static readonly	ALL_CAPS	MY_CONST_OBJECT
Boolean Variable	bCamelCase / mbPascalCase	bFired, mbIsEnabled
Boolean Property	Is/Has/Can/Should	IsFired, HasChildren

Private Member Pattern

public class OrderService
{
    // Private fields: m + PascalCase
    private readonly IOrderRepository mOrderRepository;
    private readonly ILogger mLogger;
    private int mRetryCount;
    private bool mbIsProcessing;  // boolean: mb prefix

    // Constructor parameter: camelCase (no prefix)
    public OrderService(IOrderRepository orderRepository, ILogger logger)
    {
        mOrderRepository = orderRepository;
        mLogger = logger;
    }

    // Public method: PascalCase
    public Order GetOrder(int orderId)
    {
        return getOrderInternal(orderId);
    }

    // Private method: camelCase
    private Order getOrderInternal(int orderId)
    {
        return mOrderRepository.Find(orderId);
    }
}

Enum and Struct Prefixes

// Enum: E prefix
public enum EDirection
{
    None,
    North,
    South,
    East,
    West
}

// Bit flags enum: Flags suffix
[Flags]
public enum EVisibilityFlags
{
    None = 0,
    Visible = 1,
    Hidden = 2,
    Collapsed = 4
}

// Struct: S prefix (readonly struct는 제외 가능)
public struct SUserID
{
    public int Value { get; }
}

// readonly record struct: S prefix 불필요
public readonly record struct UserID(int Value);

Nullable Naming

// Nullable parameter: OrNull suffix
public Animation GetAnimation(string nameOrNull)
{
    if (nameOrNull == null)
    {
        return DefaultAnimation;
    }
    return mAnimations[nameOrNull];
}

// Nullable return: OrNull suffix
public string GetNameOrNull()
{
    return mbHasName ? mName : null;
}

// Recursive function: Recursive suffix
public int FibonacciRecursive(int n)
{
    if (n <= 1)
    {
        return n;
    }
    return FibonacciRecursive(n - 1) + FibonacciRecursive(n - 2);
}

Code Writing Rules

Prohibited Patterns

// [WRONG] var keyword
var order = GetOrder(1);
var items = new List<Item>();

// [CORRECT] Explicit type
Order order = GetOrder(1);
List<Item> items = new List<Item>();

// [WRONG] Null coalescing operator (??)
string name = inputName ?? "Default";

// [CORRECT] Explicit null check
string name;
if (inputName != null)
{
    name = inputName;
}
else
{
    name = "Default";
}

// [WRONG] using declaration (C# 8.0)
using FileStream stream = new FileStream(path, FileMode.Open);

// [CORRECT] using statement
using (FileStream stream = new FileStream(path, FileMode.Open))
{
    // ...
}

// [WRONG] target-typed new()
List<Order> orders = new();

// [CORRECT] Explicit type
List<Order> orders = new List<Order>();

// [WRONG] Async suffix
public async Task<Order> GetOrderAsync(int id);

// [CORRECT] No Async suffix
public async Task<Order> GetOrder(int id);

// [WRONG] inline out declaration
if (int.TryParse(input, out int result))

// [CORRECT] separate out declaration
int result;
if (int.TryParse(input, out result))

Required Patterns

// Always use braces, even for single line
if (condition)
{
    DoSomething();
}

// Float literals with f suffix
float value = 0.5f;
float another = 1.0f;

// Switch must have default case
switch (status)
{
    case EStatus.Active:
        Process();
        break;
    case EStatus.Inactive:
        Skip();
        break;
    default:
        Debug.Fail("Unknown status");
        break;
}

// Debug.Assert for all assumptions
Debug.Assert(order != null, "Order should not be null");
Debug.Assert(count > 0, "Count must be positive");

// Properties instead of getter/setter methods
// [WRONG]
public int GetAge() { return mAge; }
public void SetAge(int age) { mAge = age; }

// [CORRECT] (.NET 5+ only - NOT available in Unity)
public int Age { get; private init; }

// [CORRECT] (Unity compatible)
public int Age { get; private set; }

C# 9.0 Patterns

Unity Limitation: init accessor is NOT available in Unity (requires .NET 5+ runtime). See Modern Patterns Reference for details and alternatives.

// private init (C# 9.0) - .NET 5+ only, NOT available in Unity
public class Customer
{
    public string Name { get; private init; }  // Use 'private set' in Unity
    public string Email { get; private init; }
}

// Record for immutable data
public record OrderDto(int Id, string CustomerName, decimal TotalAmount);

// Pattern matching switch expression (available in Unity)
public string GetStatusMessage(EOrderStatus status)
{
    return status switch
    {
        EOrderStatus.Pending => "Order is pending",
        EOrderStatus.Completed => "Order completed",
        _ => throw new ArgumentOutOfRangeException(nameof(status))
    };
}

Class Structure Order

public class OrderService : IOrderService
{
    // 1. Constants
    private const int MAX_RETRY_COUNT = 3;
    public static readonly TimeSpan DEFAULT_TIMEOUT = TimeSpan.FromSeconds(30);

    // 2. Private member variables
    private readonly IOrderRepository mOrderRepository;
    private readonly ILogger mLogger;
    private int mProcessedCount;
    private bool mbIsInitialized;

    // 3. Properties (with private member above if needed)
    public int ProcessedCount => mProcessedCount;
    public bool IsInitialized => mbIsInitialized;

    // 4. Constructors
    public OrderService(IOrderRepository orderRepository, ILogger logger)
    {
        mOrderRepository = orderRepository;
        mLogger = logger;
    }

    // 5. Public methods
    public Order GetOrder(int id)
    {
        Debug.Assert(id > 0, "ID must be positive");
        return mOrderRepository.Find(id);
    }

    public void ProcessOrder(Order order)
    {
        validateOrder(order);
        processInternal(order);
    }

    // 6. Private methods
    private void validateOrder(Order order)
    {
        Debug.Assert(order != null);
    }

    private void processInternal(Order order)
    {
        // Implementation
    }
}

File Organization

• 각 클래스는 독립된 파일에 작성
• 파일명 = 클래스명 (정확히 일치)
• Partial 클래스: ClassName.SubName.cs

Reference Documentation

Naming Conventions

Complete naming rules:

• m/mb 접두어 상세
• E/S 접두어 규칙
• OrNull 접미어 패턴
• ALL_CAPS 상수 규칙

Modern Patterns

C# 9.0 language features:

• Records and init-only properties
• Pattern matching
• File-scoped namespaces (C# 10)
• 금지 패턴 상세

Error Handling

Error handling patterns:

• Debug.Assert 사용
• 경계에서만 예외 처리
• null 반환/매개변수 회피
• 유효성 검증 패턴

Key Principles

1. 가독성 최우선: 명확하고 이해하기 쉬운 코드 작성
2. 명시적 타입: var 사용 금지, 타입 명시
3. Null 안전: OrNull 접미어로 nullable 명시
4. Assertion: 모든 가정에 Debug.Assert 사용
5. 경계 검증: 외부 데이터는 경계에서만 검증
6. Use init: Prefer C# 9.0 private init (.NET 5+ only, NOT available in Unity)
7. No Emoji: 코드 예제 및 문서에서 이모지 사용 금지, 텍스트 태그 사용 ([WRONG], [CORRECT], [CAUTION])