.NET Core和ASP.NET Core及WEB开发知识点

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Dependency injection into views in ASP.NET Core

Dependency injection in ASP.NET Core

Architectural principles

Write custom ASP.NET Core middleware

Service lifetimes

Choose an appropriate lifetime for each registered service. ASP.NET Core services can be configured with the following lifetimes:

Transient

Transient lifetime services (AddTransient) are created each time they're requested from the service container. This lifetime works best for lightweight, stateless services.

Scoped

Scoped lifetime services (AddScoped) are created once per client request (connection).

Warning

When using a scoped service in a middleware, inject the service into the Invoke or InvokeAsyncmethod. Don't inject via constructor injection because it forces the service to behave like a singleton. For more information, see Write custom ASP.NET Core middleware.

Singleton

Singleton lifetime services (AddSingleton) are created the first time they're requested (or when Startup.ConfigureServices is run and an instance is specified with the service registration). Every subsequent request uses the same instance. If the app requires singleton behavior, allowing the service container to manage the service's lifetime is recommended. Don't implement the singleton design pattern and provide user code to manage the object's lifetime in the class.

Warning

It's dangerous to resolve a scoped service from a singleton. It may cause the service to have incorrect state when processing subsequent requests.