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title: "Design Pattern Categories" contentKey: "design-pattern-categories" section: "getting-started" accessLevel: "free" contentType: "doc" tags: ["dotnet", "design-patterns", "categories", "getting-started"] order: 2 sourceType: "same_repo" sourcePath: "docs/free/getting-started/02-design-pattern-categories.md" routePath: "/project/dotnet-advanced-design-patterns/preview/design-pattern-categories" isPublished: true

Design Pattern Categories

This document explains the four categories of design patterns covered in this repository: the three classic GoF (Gang of Four) categories plus Enterprise/Practical patterns used in production .NET applications.

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Overview Mind Map

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Category 1: Creational Patterns

What They Solve

Creational patterns abstract the instantiation process. They help make a system independent of how its objects are created, composed, and represented.

Core Question

"How should I create this object?"

When You Need Them

• The concrete class to instantiate is determined at runtime.
• Object creation is complex (many parameters, conditional logic, expensive setup).
• You want to decouple client code from specific implementations.
• You need families of related objects that must be used together.

Patterns in This Category

Key Principle

"Program to an interface, not an implementation." Creational patterns let client code work with abstractions while the pattern handles which concrete class is actually instantiated.

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Category 2: Structural Patterns

What They Solve

Structural patterns deal with class and object composition. They help you build larger structures from individual classes and objects while keeping the structure flexible and efficient.

Core Question

"How should I compose these objects together?"

When You Need Them

• You need to integrate with a third-party library that has an incompatible interface.
• You want to add responsibilities to objects dynamically.
• You need to represent part-whole hierarchies.
• You want to simplify a complex subsystem for consumers.
• You need to share state efficiently across many objects.

Patterns in This Category

Key Principle

"Favor composition over inheritance." Structural patterns achieve flexibility by composing objects at runtime rather than locking behavior into an inheritance hierarchy at compile time.

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Category 3: Behavioral Patterns

What They Solve

Behavioral patterns are concerned with algorithms and the assignment of responsibilities between objects. They describe not just patterns of objects and classes but also the patterns of communication between them.

Core Question

"How should these objects interact and divide responsibility?"

When You Need Them

• You need to vary the algorithm used at runtime.
• You want to decouple senders from receivers.
• You need to traverse or operate on complex structures.
• You want to model state-dependent behavior.
• You need undo/redo functionality.
• You want to define a processing pipeline.

Patterns in This Category

Key Principle

"Encapsulate what varies." Behavioral patterns identify the aspects of your application that vary and separate them from what stays the same.

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Category 4: Enterprise / Practical Patterns

What They Solve

Enterprise patterns address concerns that emerge in real-world, production-grade applications — data access, distributed systems, configuration management, and domain modeling. They are not part of the original GoF catalog but are essential knowledge for any professional .NET developer.

Core Question

"How should I architect the layers and infrastructure of a production system?"

When You Need Them

• You need a clean data access layer that is testable and swappable.
• You must ensure transactional consistency across multiple repository operations.
• You want to express domain logic as composable, testable rules.
• You need to handle errors gracefully without exception-based control flow.
• You must guarantee event delivery in distributed systems.
• You want type-safe configuration with validation.

Patterns in This Category

Key Principle

"Make the implicit explicit." Enterprise patterns take concerns that are often buried in infrastructure code (transactions, event delivery, configuration) and make them first-class, testable, documented parts of your architecture.

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How the Categories Relate

Progression Path

1. Creational patterns get the right objects into existence.
2. Structural patterns connect those objects into useful structures.
3. Behavioral patterns define how those structures communicate and process work.
4. Enterprise patterns combine all of the above into production architectures.

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Category Comparison Table

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Next Steps

• Creational Patterns Summary
• Structural Patterns Summary
• Behavioral Patterns Summary
• Enterprise Patterns Summary
• Pattern Selection Guide