Professional C# 7 and .NET Core 2.0, 7th Edition

20Dependency Injection

WHAT’S IN THIS CHAPTER?

• Defining dependency injection
• Using dependency injection with Microsoft.Extensions.DependencyInjection
• Working with lifetime of services
• Using options and configuration to initialize services
• Using DI to create platform independence for WPF, UWP, and Xamarin
• Using other dependency injection containers

WROX.COM CODE DOWNLOADS FOR THIS CHAPTER

The wrox.com code downloads for this chapter are found at www.wrox.com on the Download Code tab. The source code is also available at https://github.com/ProfessionalCSharp/ProfessionalCSharp7 in the directory DependencyInjection. The code for this chapter is divided into the following major examples:

• NoDI
• WithDI
• WithDIContainer
• ServicesLifetime
• DIWithOptions
• DIWithConfigurations
• PlatformIndependenceSample
• DIWithAutofac

WHAT IS DEPENDENCY INJECTION?

Faster development cycles demand unit tests and better updatability. Making some code changes should not result in errors in unexpected places. Creating more modular applications where dependencies are reduced helps with that.

Dependency injection (DI) allows injection dependencies from the outside of a class, thus the class where the dependency is injected only needs to know about a contract (usually a C# interface). The class can be independent of the creation of its objects.

Dependency injection allows for easier unit tests. With the unit test, only a specific class needs testing, and the dependencies needed can be replaced by a special ...