2nd/10_Wiki/Topics/Topic_Programming/Topic_CSharp/CSharp_Abstract.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-abstract	C# Abstraction	Programming_Language	draft	conceptual		abstract class method C# C# 추상화		B	0.85	2026-07-04	2026-07-04			csharp programming-language w3schools oop abstraction	https://www.w3schools.com/cs/cs_abstract.php

CSharp Abstraction

🎯 한 줄 통찰 (One-line insight)

Where C++ makes a class abstract IMPLICITLY (simply by containing at least one pure virtual function written as virtual void f() = 0;, with no dedicated "this class is abstract" keyword), C# makes it EXPLICIT with a dedicated abstract keyword on both the class AND each bodyless method (abstract class Animal { public abstract void animalSound(); }) — the same underlying restriction (cannot instantiate, must be inherited to be used, subclass MUST supply the missing method body) is enforced, but C# spells out the intent in the declaration itself rather than deriving it as a side-effect of the method's syntax. [S1]

🧠 핵심 개념 (Core concepts)

• Data abstraction — hiding certain implementation details, showing only essential information to the user; achievable via abstract classes OR interfaces (interfaces deferred to the next chapter). [S1]
• abstract on a class — creates a RESTRICTED class that cannot be used to instantiate objects directly (new Animal() on an abstract class is a compile error: "Cannot create an instance of the abstract class or interface"). [S1]
• abstract on a method — declared with NO body (just a signature ending in ;); only legal inside an abstract class; the body must be supplied by whichever derived class inherits it, using override. [S1]
• Mixed abstract classes — an abstract class can freely combine abstract methods (no body) alongside regular, fully-implemented methods. [S1]
• Must be accessed via inheritance — the ONLY way to use an abstract class's functionality is to inherit from it and instantiate the DERIVED class instead. [S1]

📖 세부 내용 (Details)

• Illegal direct instantiation: abstract class Animal { public abstract void animalSound(); public void sleep() { Console.WriteLine("Zzz"); } } ... Animal myObj = new Animal(); // Error. [S1]
• Full working example (Animal converted from the Polymorphism chapter into an abstract class): abstract class Animal { public abstract void animalSound(); public void sleep() { Console.WriteLine("Zzz"); } } class Pig : Animal { public override void animalSound() { Console.WriteLine("The pig says: wee wee"); } } ... Pig myPig = new Pig(); myPig.animalSound(); myPig.sleep(); — the abstract method's body comes entirely from Pig, while sleep() (a regular method) is inherited unchanged. [S1]
• Purpose stated directly: achieving security by hiding certain details and showing only the important parts of an object. [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

• abstract가 클래스에도 명시적 키워드로 붙음: C++는 순수 가상 함수(virtual void f() = 0;) 하나만 있어도 클래스가 암묵적으로 추상 클래스가 되고 별도의 "추상 클래스" 키워드가 없었지만, C#은 클래스 자체에도 abstract 키워드를 명시적으로 붙여야 한다는 점이 확인됨 — 같은 제약(인스턴스화 불가, 상속 필수, 파생 클래스가 반드시 구현 제공)을 표현하는 방식이 암묵적(C++) vs 명시적(C#)으로 다름. [S1]
• Polymorphism 챕터의 Animal 예제가 그대로 재사용됨: 새로운 예제를 만들지 않고 직전 Polymorphism 챕터의 Animal/Pig 예제를 abstract로 변환해 재사용한다는 점이 확인됨 — 개념을 처음부터 다시 설명하지 않고 이미 익힌 코드를 확장하는 방식. [S1]

🛠️ 적용 사례 (Applied in summary)

추상 메서드 animalSound()와 일반 메서드 sleep()을 함께 가진 abstract class Animal을 Pig가 상속해 animalSound()의 몸체만 제공하고 sleep()은 그대로 물려받아 쓰는 예제가 원문에서 직접 실전 활용 사례로 제시됨. [S1]

💻 코드 패턴 (Code patterns)

Abstract class mixing an abstract method (no body) and a regular method (C#):

abstract class Animal
{
    public abstract void animalSound();  // no body -- must be overridden
    public void sleep()                   // regular method -- inherited as-is
    {
        Console.WriteLine("Zzz");
    }
}
class Pig : Animal
{
    public override void animalSound()
    {
        Console.WriteLine("The pig says: wee wee");
    }
}

Pig myPig = new Pig();
myPig.animalSound(); // "The pig says: wee wee"
myPig.sleep();        // "Zzz"

✅ 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 Polymorphism, CSharp Interface, CPP Templates
• 참조 맥락: Polymorphism & Abstract 섹션의 마지막 챕터 — Interface 섹션으로 이어짐.

📚 출처 (Sources)

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

📝 변경 이력 (Change history)

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