---
id: csharp-interface-multi
title: "C# Multiple Interfaces"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["implement multiple interfaces C#", "C# 다중 인터페이스"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.83
created_at: 2026-07-04
updated_at: 2026-07-04
review_reason: ""
merge_history: []
tags: ["csharp", "programming-language", "w3schools", "oop", "interface"]
raw_sources: ["https://www.w3schools.com/cs/cs_interface_multi.php"]
applied_in: []
github_commit: ""
---

# [[CSharp Interface Multi]]

## 🎯 한 줄 통찰 (One-line insight)
This short chapter delivers exactly the payoff the previous Interface chapter promised: a single class implementing MULTIPLE interfaces via a comma-separated list after `:` (`class DemoClass : IFirstInterface, ISecondInterface`) — this is as close as C# gets to C++'s multiple inheritance, but the constraint is real: every interface in the list contributes only bodyless method signatures, never actual field data or base implementation, so C# is achieving multiple "contracts" rather than C++'s multiple actual base-class STATE and behavior. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Comma-separated interface list** — `class DemoClass : IFirstInterface, ISecondInterface { ... }` — any number of interfaces can follow the `:`. [S1]
- **Each interface method must be implemented** — the implementing class must provide a body for every method declared across ALL implemented interfaces. [S1]
- **Still no shared state from interfaces** — since interfaces can't contain fields (per the previous chapter), implementing multiple interfaces never brings in multiple sets of DATA, only multiple sets of METHOD CONTRACTS. [S1]

## 📖 세부 내용 (Details)
- Two interfaces: `interface IFirstInterface { void myMethod(); } interface ISecondInterface { void myOtherMethod(); }`. [S1]
- Combined implementation: `class DemoClass : IFirstInterface, ISecondInterface { public void myMethod() { Console.WriteLine("Some text.."); } public void myOtherMethod() { Console.WriteLine("Some other text..."); } }`. [S1]
- Usage: `DemoClass myObj = new DemoClass(); myObj.myMethod(); myObj.myOtherMethod();` → prints both messages. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **C++ 다중 상속의 데이터 상속과 달리 계약(메서드 시그니처)만 상속됨**: C++의 다중 상속(`[[CPP Inheritance Multiple]]`)은 여러 베이스 클래스의 실제 필드와 구현을 함께 물려받았지만, C#의 다중 인터페이스 구현은 인터페이스가 필드를 가질 수 없으므로 메서드 시그니처(계약)만 여러 개 물려받는다는 점이 확인됨 — 실질적으로 더 제한된 형태의 "다중 상속". [S1]

## 🛠️ 적용 사례 (Applied in summary)
IFirstInterface와 ISecondInterface 두 인터페이스를 DemoClass 하나가 동시에 구현해 두 메서드를 모두 호출하는 예제가 원문에서 직접 실전 활용 사례로 제시됨. [S1]

## 💻 코드 패턴 (Code patterns)
Implementing two interfaces in one class, comma-separated (C#):
```csharp
interface IFirstInterface { void myMethod(); }
interface ISecondInterface { void myOtherMethod(); }

class DemoClass : IFirstInterface, ISecondInterface
{
    public void myMethod() { Console.WriteLine("Some text.."); }
    public void myOtherMethod() { Console.WriteLine("Some other text..."); }
}
```

## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual
- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
- **신뢰 점수:** 0.83
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[C# Tutorial]]
- **관련 개념:** [[CSharp Interface]], [[CSharp Enums]], [[CPP Inheritance Multiple]]
- **참조 맥락:** Interface 섹션의 마지막 챕터 — Enums 섹션으로 이어짐.

## 📚 출처 (Sources)
- [S1] W3Schools — C# Multiple Interfaces — https://www.w3schools.com/cs/cs_interface_multi.php

## 📝 변경 이력 (Change history)
- 2026-07-04: Initial draft synthesized from the W3Schools "C# Multiple Interfaces" page (Astra wiki-curation, P-Reinforce v3.1 format).