csharp-async-patterns

C# Async/Await Patterns

Overview

C# 비동기 프로그래밍 패턴 (POCU 표준 적용)

Foundation Required: csharp-code-style (mPascalCase, Async 접미사 금지, var 금지)

Core Topics:

async/await 기본
CancellationToken 패턴
ConfigureAwait 사용법
비동기 에러 처리
Task 조합 및 조율
ValueTask 최적화

Quick Start

public class DataService { private readonly IDataRepository mRepository; private readonly ILogger mLogger;

public DataService(IDataRepository repository, ILogger logger)
{
    mRepository = repository;
    mLogger = logger;
}

// ✅ POCU: Async 접미사 없음
public async Task&#x3C;Data> LoadData(CancellationToken ct = default)
{
    try
    {
        Data data = await mRepository.Fetch(ct);
        return processData(data);
    }
    catch (OperationCanceledException)
    {
        mLogger.Info("Operation cancelled");
        throw;
    }
}

private Data processData(Data data)
{
    Debug.Assert(data != null);
    // Processing logic
    return data;
}

}

Key Rules (POCU)

Async 메서드 명명

// ❌ WRONG: Async 접미사 사용 public async Task<Order> GetOrderAsync(int id); public async Task SaveOrderAsync(Order order);

// ✅ CORRECT: Async 접미사 없음 public async Task<Order> GetOrder(int id); public async Task SaveOrder(Order order);

async void 금지

// ❌ WRONG: async void public async void LoadData() { await mRepository.Fetch(); }

// ✅ CORRECT: async Task public async Task LoadData() { await mRepository.Fetch(); }

// ⚠️ EXCEPTION: 이벤트 핸들러만 async void 허용 private async void OnButtonClick(object sender, EventArgs e) { try { await ProcessClick(); } catch (Exception ex) { mLogger.Error(ex, "Click handler failed"); } }

명시적 타입 사용

// ❌ WRONG: var 사용 var result = await GetOrder(1); var tasks = new List<Task>();

// ✅ CORRECT: 명시적 타입 Order result = await GetOrder(1); List<Task> tasks = new List<Task>();

using 문 사용

// ❌ WRONG: using 선언 using CancellationTokenSource cts = new CancellationTokenSource(timeout);

// ✅ CORRECT: using 문 using (CancellationTokenSource cts = new CancellationTokenSource(timeout)) { return await LoadData(cts.Token); }

CancellationToken 패턴

public class OrderProcessor { private readonly IOrderRepository mRepository;

// 항상 CancellationToken 지원
public async Task&#x3C;Order> ProcessOrder(int orderId, CancellationToken ct = default)
{
    ct.ThrowIfCancellationRequested();

    Order order = await mRepository.GetOrder(orderId, ct);
    Debug.Assert(order != null);

    await validateOrder(order, ct);
    await calculateTotal(order, ct);
    await mRepository.SaveOrder(order, ct);

    return order;
}

private async Task validateOrder(Order order, CancellationToken ct)
{
    Debug.Assert(order != null);
    await mRepository.ValidateInventory(order.Items, ct);
}

private async Task calculateTotal(Order order, CancellationToken ct)
{
    Debug.Assert(order != null);
    decimal total = 0;
    foreach (OrderItem item in order.Items)
    {
        ct.ThrowIfCancellationRequested();
        total += item.Price * item.Quantity;
    }
    order.Total = total;
}

}

Reference Documentation

Best Practices

Essential patterns for async/await:

CancellationToken 사용 패턴
ConfigureAwait 가이드라인
async void 회피
예외 처리

Code Examples

Comprehensive code examples:

기본 비동기 작업
병렬 실행 패턴
타임아웃 및 재시도
고급 패턴

Anti-Patterns

Common mistakes to avoid:

.Result, .Wait() 차단
Fire-and-forget 오류 처리 누락
CancellationToken 미전파

Key Principles

Async All the Way: 비동기 호출 체인 유지
Always Support Cancellation: 장기 실행 작업은 CancellationToken 필수
ConfigureAwait in Libraries: 라이브러리 코드에서 ConfigureAwait(false) 사용
No Async Suffix: POCU 표준 - Async 접미사 금지
No async void: 이벤트 핸들러 외 async void 금지
Explicit Types: var 대신 명시적 타입 사용

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