🏫 School System — OOP in C#

A didactic project demonstrating the four pillars of Object-Oriented Programming in C#.

📁 Project Structure

SchoolSystem/
├── Interfaces/
│   ├── IEvaluable.cs      → Contract: CalculateAverage() and GetGrade()
│   └── IReport.cs         → Contract: GenerateReport()
├── Models/
│   ├── Person.cs          → ABSTRACT class (base for Student and Teacher)
│   ├── Student.cs         → Inherits Person, implements IEvaluable and IReport
│   └── Teacher.cs         → Inherits Person, implements IReport
├── Services/
│   └── Classroom.cs       → Groups Students and Teacher, implements IReport
├── Program.cs             → Entry point — demonstrates all concepts
└── SchoolSystem.csproj

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🧠 Concepts Demonstrated

1. 🔒 Encapsulation

• Private fields (_name, _ssn, _grades) exposed only through controlled properties
• Setters with validation (e.g. SSN with 9 digits, grades between 0 and 10)
• Internal logic protected (enrollment ID generation, salary calculation by experience)

// Grades can only be added via method — which validates the value
student.AddGrade(8.5);  // ✅ OK
student.AddGrade(15);   // ❌ Throws exception

2. 🧬 Inheritance

• Student and Teacher both inherit from Person (abstract class)
• Constructors use base(...) to reuse the parent class logic
• protected modifier allows controlled access in subclasses

public class Student : Person { ... }
public class Teacher : Person { ... }

3. 🎭 Polymorphism

• Introduce() is virtual in Person and overridden in Student and Teacher
• GetType() is abstract: forces each subclass to provide its own implementation
• A List<Person> can hold Students and Teachers — the correct method is called at runtime

List<Person> people = new() { teacher, student1, student2 };
foreach (var p in people)
    Console.WriteLine(p.Introduce()); // Each one responds differently!

4. 🔌 Interfaces & Abstractions

• IEvaluable → implemented only by Student (has grades and an average)
• IReport → implemented by Student, Teacher, and Classroom
• Allows different objects to be treated uniformly via the interface type

List<IReport> reports = new() { teacher, student, classroom };
foreach (var r in reports)
    Console.WriteLine(r.GenerateReport()); // Each generates its own

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▶️ How to Run

cd SchoolSystem
dotnet run

Requirement: .NET 8 SDK