_Dependency_Injection_Patterns

Next Topic: API Design Principles and Best Practices Cheat Sheet

Category: Software Engineering | Subcategory: Design Patterns
Last Updated: 2026-05-16

What This Cheat Sheet Covers

This topic spans 15 focused tables and 150 indexed concepts. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.

Table 1: Core DI ConceptsTable 2: Injection TypesTable 3: DI Container FeaturesTable 4: Service LifetimesTable 5: Framework Implementations - SpringTable 6: Framework Implementations - .NETTable 7: Framework Implementations - NestJSTable 8: Framework Implementations - Angular & Java CDITable 9: Lifetime Management & ScopingTable 10: Testing with DITable 11: Anti-Patterns & Code SmellsTable 12: Advanced DI PatternsTable 13: Container Comparison & PerformanceTable 14: Best Practices & Design GuidelinesTable 15: Common DI Scenarios & Solutions

Overview

Dependency Injection (DI) is a design pattern and software engineering technique that implements Inversion of Control (IoC) for resolving dependencies. DI allows objects to receive their dependencies from external sources rather than creating them internally, promoting loose coupling, testability, and maintainability in software systems.

Table 1: Core DI Concepts

Before reaching for a container or an annotation, it helps to nail down the vocabulary everyone uses loosely. These are the building blocks — what a dependency actually is, where it gets wired (the composition root), why we favor loose coupling over new, and how registration and resolution turn abstractions into running objects.

Concept	Example	Description
Dependency Injection	Service receives database connection via constructor instead of creating it	Pattern where dependencies are provided to a class from external sources rather than being created internally
Inversion of Control (IoC)	Framework manages object instantiation and disposal instead of manual new/delete	Principle where control of object creation and lifecycle is transferred from the application to a framework/container
Service Locator	ServiceLocator.Get<ILogger>() vs constructor injection	Anti-pattern where a centralized registry provides dependencies on demand (discouraged vs DI)
Composition Root	Main() method or Startup.cs where DI container is configured	Single location in application where object graphs are assembled and dependencies wired together
DI Container	Spring ApplicationContext, .NET IServiceProvider, NestJS Module system	Framework that manages dependency resolution, object creation, and lifecycle management

Overview

Table 1: Core DI Concepts

Concept	Example	Description
Dependency Injection	Service receives database connection via constructor instead of creating it	Pattern where dependencies are provided to a class from external sources rather than being created internally
Inversion of Control (IoC)	Framework manages object instantiation and disposal instead of manual new/delete	Principle where control of object creation and lifecycle is transferred from the application to a framework/container
Service Locator	ServiceLocator.Get<ILogger>() vs constructor injection	Anti-pattern where a centralized registry provides dependencies on demand (discouraged vs DI)
Composition Root	Main() method or Startup.cs where DI container is configured	Single location in application where object graphs are assembled and dependencies wired together
DI Container	Spring ApplicationContext, .NET IServiceProvider, NestJS Module system	Framework that manages dependency resolution, object creation, and lifecycle management

Dependency Injection Patterns

Overview

Table 1: Core DI Concepts

Dependency Injection Patterns

Overview

Table 1: Core DI Concepts