2nd/10_Wiki/Topics/Domain_Programming/Topic_CSharp/CSharp_Interface.md

id, title, category, status, verification_status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, created_at, updated_at, review_reason, merge_history, tags, raw_sources, applied_in, github_commit

id	title	category	status	verification_status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	created_at	updated_at	review_reason	merge_history	tags	raw_sources	applied_in	github_commit
csharp-interface	C# Interface	Programming_Language	draft	conceptual		interface implements C# IAnimal C# 인터페이스		B	0.85	2026-07-04	2026-07-04			csharp programming-language w3schools oop interface	https://www.w3schools.com/cs/cs_interface.php

CSharp Interface

🎯 한 줄 통찰 (One-line insight)

The tutorial states outright why interfaces exist at all: "C# does not support 'multiple inheritance' (a class can only inherit from ONE base class)" — a hard restriction with NO equivalent in Topic_CPP, where C++ freely supports true multiple class inheritance (class Derived : public Base1, public Base2, already documented in [[CPP Inheritance Multiple]]) — so C# compensates by letting a class implement MANY interfaces via the SAME : syntax used for single-class inheritance, making interfaces less a stylistic alternative to abstract classes and more a structural workaround for a capability C# deliberately doesn't offer at the class level. [S1]

🧠 핵심 개념 (Core concepts)

• Interface — a "completely abstract class" containing ONLY abstract methods and properties with empty bodies; no fields/variables allowed. [S1]
• Naming convention — interfaces are conventionally prefixed with I (e.g. IAnimal) to distinguish them from ordinary classes at a glance. [S1]
• Default member modifiers — interface members are implicitly abstract AND public, with no need to write those keywords. [S1]
• Implementation via : — the SAME symbol used for inheritance; a class "implements" an interface using :, and must provide bodies for ALL the interface's methods. [S1]
• No override keyword needed — unlike overriding a virtual base method, implementing an interface method requires no override keyword at all. [S1]
• Cannot instantiate an interface directly — like an abstract class, an interface can never be new'd into an object. [S1]
• No constructors — an interface cannot have a constructor, since it can never be instantiated. [S1]
• Motivation #2, stated explicitly — because C# disallows multiple class inheritance, interfaces are the mechanism for achieving multiple-inheritance-like behavior (a class implementing several interfaces). [S1]

📖 세부 내용 (Details)

• Interface declaration: interface Animal { void animalSound(); void run(); } — both methods bodyless. [S1]
• Implementation: interface IAnimal { void animalSound(); } class Pig : IAnimal { public void animalSound() { Console.WriteLine("The pig says: wee wee"); } } ... Pig myPig = new Pig(); myPig.animalSound();. [S1]
• Explicit note that IAnimal myObj = new IAnimal(); would be impossible, mirroring the abstract class restriction. [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

• 다중 상속 부재를 인터페이스로 보완함: C++는 class Derived : public Base1, public Base2처럼 여러 클래스를 동시에 상속하는 진짜 다중 상속을 지원했지만([[CPP Inheritance Multiple]]), C#은 클래스 단위 다중 상속을 아예 지원하지 않고 대신 여러 인터페이스를 구현(implement)하는 방식으로 유사한 효과를 낸다는 점이 원문에서 직접 그 이유로 명시됨. [S1]
• 인터페이스 구현에는 override가 필요 없음: Abstract 챕터에서 abstract 클래스를 상속할 때는 override 키워드가 필수였지만, 인터페이스를 implement할 때는 override 없이 그냥 메서드를 정의하면 된다는 차이가 확인됨. [S1]

🛠️ 적용 사례 (Applied in summary)

IAnimal 인터페이스의 animalSound() 메서드를 Pig 클래스가 override 없이 그대로 구현해 호출하는 예제가 원문에서 직접 실전 활용 사례로 제시됨. [S1]

💻 코드 패턴 (Code patterns)

Interface implementation — no override keyword required (C#):

interface IAnimal
{
    void animalSound(); // no body
}
class Pig : IAnimal    // "implements" -- same : syntax as inheritance
{
    public void animalSound()   // no `override` needed
    {
        Console.WriteLine("The pig says: wee wee");
    }
}

Pig myPig = new Pig();
myPig.animalSound();

✅ 검증 상태 및 신뢰도

• 상태: draft
• 검증 단계: conceptual
• 출처 신뢰도: B (W3Schools — widely used educational reference, not a primary standards body)
• 신뢰 점수: 0.85
• 중복 검사 결과: 신규 생성 (New discovery)

🔗 지식 그래프 (Knowledge Graph)

• 상위/루트: C# Tutorial
• 관련 개념: CSharp Abstract, CSharp Interface Multi, CPP Inheritance Multiple
• 참조 맥락: Interface 섹션 — Multiple Interfaces 챕터로 이어짐.

📚 출처 (Sources)

• [S1] W3Schools — C# Interface — https://www.w3schools.com/cs/cs_interface.php

📝 변경 이력 (Change history)

• 2026-07-04: Initial draft synthesized from the W3Schools "C# Interface" page (Astra wiki-curation, P-Reinforce v3.1 format).