Want to write clean, scalable, and maintainable C# code ? Let’s break down the OOP fundamentals and the SOLID design principles — with real-world examples, explanations, and code snippets you can copy-paste into your next project. 📚 Table of Contents 🎯 OOP fundamentals 🔒 Encapsulation 🎭 Abstraction 🧬 Inheritance 🔄 Polymorphism 🏗️ SOLID principles S — Single Responsibility Principle O — Open/Closed Principle L — Liskov Substitution Principle I — Interface Segregation Principle D — Dependency Inversion Principle 🛒 Mini e-commerce scenario (tying everything together) 💡 Next steps (make it runnable!) 🎯 1. OOP Fundamentals 🔒 Encapsulation — protect your object’s state 👉 Idea: Don’t let anyone mess with your object’s internals. Provide safe, controlled methods. Use-case: An Order should manage its own items and discounts. public class Order { private readonly List<OrderItem> _items = new(); private decimal _discountPercent; publ...
Azure Entra ID (formerly Azure Active Directory) is Microsoft’s cloud-based identity and access management (IAM) service. It helps secure apps, APIs, and services by managing authentication (who you are) and authorization (what you can do) . 🔹 1. Key Concepts Tenant : A dedicated instance of Entra ID for your organization. App Registration : Register apps to integrate with Entra ID for authentication. Authentication : Verifying user or service identity (via username, password, certificate, token). Authorization : Granting permissions (roles/scopes) after authentication. Tokens : ID Token → User identity (used in login). Access Token → Grants access to APIs. Refresh Token → Get new tokens without logging in again. 🔹 2. Authentication Flows Authorization Code Flow (with PKCE) – Secure for web & mobile apps. Client Credentials Flow – Service-to-service authentication (no user). Device Code Flow – Used on devices without browsers (IoT, CLI). Implicit Flo...