How deeply does ASP.NET Core in Action, 3e cover AddSingleton?

Defines singleton lifetime and demonstrates type and object registration, but defers detailed lifetime discussion and asynchronous factories.

AddSingleton

As explained in ASP.NET Core in Action, 3e

AddSingleton is an ASP.NET Core service-registration method that registers a service with singleton lifetime.

AddSingleton is an ASP.NET Core dependency-injection registration method. It tells the built-in DI container to use one instance of a service throughout the application. section 9.1 section 9.2

Use AddSingleton in these forms:

Register a concrete type directly: builder.Services.AddSingleton<MessageFactory>(); The container creates and reuses the registered type. section 9.1
Register an existing object: builder.Services.AddSingleton(new EmailServerSettings("smtp.server.com", 25)); The supplied object is always treated as a singleton. section 9.2
Choose another lifetime when each request needs a newly created object; a factory lambda can be registered with AddScoped instead. section 9.2

Registering a shared service

WebApplicationBuilder builder = WebApplication.CreateBuilder(args); builder.Services.AddSingleton<MessageFactory>(); WebApplication app = builder.Build(); The container can now create MessageFactory when a dependency requires it and reuse the same instance throughout the application.

How ASP.NET Core in Action, 3e covers it

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Pro ASP.NET Core 7, Tenth EditionAddSingleton is an ASP.NET Core dependency-injection registration method that reuses one service instance for the lifetime of the application.

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Related concepts

Singleton patternconfigures · The Singleton pattern restricts a type or component to one shared instance within a defined scope and provides a way to access it.
dependency injectionconfigures · Dependency injection is a software design technique in which a component receives its dependencies from outside rather than creating or locating them internally.

This explainer was generated by Manning's knowledge graph from the text of ASP.NET Core in Action, 3e. The section links point to the parts of the book it draws on.