Dependency Injection vs Service Locator - Best Practice

Lars-Erik KindbladSenior ConsultantBlog: kindblad.com

Dependency Injection vs. Service Locator- Best Practice

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Agenda

Intro• Inversion of Control• Dependency Injection Patterns• Service Locator Patterns• Inversion of Control Containers

Best Practice• What patterns to use• When to use the patterns

Summary

Inversion of Control

Inversion of Control = IOC Make code loosely coupled Make unit testing possible How? Move creation of dependencies outside the class they are

being used in A better name - Inversion of Dependency Creation

Traditional Code

Inversion of Control

Traditional Code

Inversion of Control Code

Traditional Code

Dependency Injection - Constructor Injection

Dependency Injection - Interface Injection

Dependency Injection - Setter Injection

Static Service Locator

Injected Service Locator

Inversion of Control Container

A framework that can automatically create a given type with all the required dependencies

Popular frameworks• Unity• Castle Windsor• Ninject• StructureMap• etc.

Inversion of Control Container

Manual approach

Using an IOC Container

Which patterns to use

Traditional Code

Dependency Injection - Constructor Injection

Dependency Injection - Interface Injection

Dependency Injection - Setter Injection

Static Service Locator

Injected Service Locator

When to use which patterns

Always use Dependency Injection – Constructor Injection

...except

FACADE CLASSES

Facade Classes

Dependency Injection

Service Locator

Dependency Injection using Func<>

BASE CLASSES

Base Classes

Service Locator

UNKNOWN TYPES AT COMPILE TIME

Unknown types at compile time

Service Locator

Summary

Constructor Injection Injected Service Locator

Facade classes(WCF Services,MVC Controllers)

Loops X (Func<>) X

Base classes X

Unknown types at compile time

All other scenarios X

QUESTIONS?

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Dependency Injection vs Service Locator - Best Practice

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Transcript of Dependency Injection vs Service Locator - Best Practice

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