Design Patterns Mastery
1. Introduction to Design Patterns
Introduction to GoF Patterns: Why patterns matter? SOLID Principles: The foundation of all patterns DRY, KISS, and YAGNI (Architectural Philosophy)
2. Creational Patterns
Singleton Pattern: Thread-safety & Captive Dependencies Factory Method: Abstracting complex object creation Abstract Factory: Creating families of related objects Builder Pattern: Constructing complex fluents Prototype Pattern: Cloning high-cost objects
3. Structural Patterns
Adapter Pattern: Bridging incompatible interfaces Bridge Pattern: Decoupling abstraction from implementation Composite Pattern: Managing tree structures & hierarchies Decorator Pattern: Enhancing behavior without inheritance Facade Pattern: Simplifying complex library subsystems Flyweight Pattern: Drastically reducing memory footprint Proxy Pattern: Interception, Lazy-Loading, and Security
4. Behavioral Patterns
Chain of Responsibility: Middleware & Pipeline Architecture Command Pattern: Implementing Undo/Redo & Queueing Interpreter Pattern: Building domain-specific languages Iterator Pattern: Unified traversal of collections Mediator Pattern: Decoupling components with MediatR Memento Pattern: Capturing and restoring object state Observer Pattern: Pub/Sub & Event-driven architecture State Pattern: Managing complex object lifecycles Strategy Pattern: Swappable algorithms at runtime Template Method: Defining skeleton algorithms Visitor Pattern: Separating operations from data structures
5. Modern Enterprise & Cloud Patterns
Repository & Unit of Work (The EF Core Standard) CQRS Pattern (Command Query Responsibility Segregation) Circuit Breaker & Retry Patterns (Resilience with Polly) Dependency Injection Pattern (The Modern King)
Design Patterns Mastery

SOLID Principles: The foundation of all patterns

1 Views Updated 5/4/2026

The SOLID Principles

Before you can master design patterns, you must master SOLID. These five principles are the "Constitution" of Object-Oriented Programming. If you follow them, your code becomes naturally extensible, testable, and maintainable.

1. S: Single Responsibility (SRP)

A class should have one, and only one, reason to change. If a class handles database logic AND email notifications, it's violating SRP. Split them.

2. O: Open/Closed Principle (OCP)

Code should be Open for extension, but Closed for modification. You should be able to add new features by adding new classes, NOT by editing existing ones. Patterns like Strategy and Decorator are built on this principle.

3. L: Liskov Substitution (LSP)

Objects of a superclass should be replaceable with objects of its subclasses without breaking the application. Don't inherit if you have to throw NotImplementedException in the child class!

4. I: Interface Segregation (ISP)

A client should never be forced to depend on methods it does not use. Large interfaces should be split into smaller, more specific ones (e.g., IReader and IWriter instead of a single IFileHandler).

5. D: Dependency Inversion (DIP)

High-level modules should not depend on low-level modules. Both should depend on Abstractions (Interfaces). This is the foundation of Dependency Injection.

4. Interview Mastery

Q: "What is the difference between 'Dependency Inversion' and 'Dependency Injection'?"

Architect Answer: "They are often confused but fundamentally different. **Dependency Inversion** is the high-level *Principle* (the 'D' in SOLID) that tells us to depend on abstractions. **Dependency Injection** is a specific *Pattern* or *Technique* used to implement that principle by passing (injecting) those abstractions into a class's constructor at runtime."

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Design Patterns Mastery
1. Introduction to Design Patterns
Introduction to GoF Patterns: Why patterns matter? SOLID Principles: The foundation of all patterns DRY, KISS, and YAGNI (Architectural Philosophy)
2. Creational Patterns
Singleton Pattern: Thread-safety & Captive Dependencies Factory Method: Abstracting complex object creation Abstract Factory: Creating families of related objects Builder Pattern: Constructing complex fluents Prototype Pattern: Cloning high-cost objects
3. Structural Patterns
Adapter Pattern: Bridging incompatible interfaces Bridge Pattern: Decoupling abstraction from implementation Composite Pattern: Managing tree structures & hierarchies Decorator Pattern: Enhancing behavior without inheritance Facade Pattern: Simplifying complex library subsystems Flyweight Pattern: Drastically reducing memory footprint Proxy Pattern: Interception, Lazy-Loading, and Security
4. Behavioral Patterns
Chain of Responsibility: Middleware & Pipeline Architecture Command Pattern: Implementing Undo/Redo & Queueing Interpreter Pattern: Building domain-specific languages Iterator Pattern: Unified traversal of collections Mediator Pattern: Decoupling components with MediatR Memento Pattern: Capturing and restoring object state Observer Pattern: Pub/Sub & Event-driven architecture State Pattern: Managing complex object lifecycles Strategy Pattern: Swappable algorithms at runtime Template Method: Defining skeleton algorithms Visitor Pattern: Separating operations from data structures
5. Modern Enterprise & Cloud Patterns
Repository & Unit of Work (The EF Core Standard) CQRS Pattern (Command Query Responsibility Segregation) Circuit Breaker & Retry Patterns (Resilience with Polly) Dependency Injection Pattern (The Modern King)