Professional C# and .NET, 2021st Edition

15Dependency Injection and Configuration

WHAT'S IN THIS CHAPTER?

• Understanding dependency injection
• Configuring the DI Container with the host class
• Managing the lifetime of services
• Disposing services
• Using options and configuration to initialize services
• Handling configuration with .NET applications
• Working with user secrets
• Using Azure App Configuration

CODE DOWNLOADS FOR THIS CHAPTER

The source code for this chapter is available on the book page at www.wiley.com. Click the Downloads link. The code can also be found at https://github.com/ProfessionalCSharp/ProfessionalCSharp2021 in the 2_Libs/DependencyInjectionAndConfiguration folder.

The code for this chapter is divided into the following major examples:

• WithDIContainer
• WithHost
• ServicesLifetime
• DIWithOptions
• DIWithConfiguration
• ConfigurationSample
• AzureAppConfigWebApp

All the projects have nullable reference types enabled.

WHAT IS DEPENDENCY INJECTION?

Faster development cycles demand unit tests and better updatability. Making some code changes should not result in errors where you don't expect them. Creating more modular applications where dependencies are reduced helps with that.

Dependency injection (DI) is a pattern where an object receives other objects it depends on—instead of creating it on its own. This reduces dependencies, because the receiving object doesn't need to know about the details of the object it receives; all it needs is a contract (usually a C# interface).

Dependency injection ...