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Day 04Sprint 1 • C# 12 Core
2 Hours
Day 4: Object-Oriented Principles, Interfaces & Dependency Inversion
Enterprise applications never couple high-level business logic directly to low-level implementation details. By coding against interfaces rather than concrete classes, your software becomes easily testable, maintainable, and open for extension without modifying existing code.
Master the 4 OOP Pillars (Encapsulation, Abstraction, Inheritance, Polymorphism)
Design robust contracts using C# interfaces (ILogger, INotificationService)
Implement the Dependency Inversion Principle (SOLID) for loose coupling
Build a pluggable payment processor supporting PayPal, UPI & CreditCard
Core Architectural Insights
- An interface defines a contract without implementation details
- Classes can implement multiple interfaces
- Dependency Inversion: High-level modules should depend on abstractions, not concretions
- Polymorphism enables treating different payment gateways uniformly via IPaymentGateway
Real-World Developer Analogy
A wall electrical socket is an interface. A phone charger, laptop adapter, or lamp can all plug into it because they adhere to the same socket specification.