2 - [Updated] - ASP .Net core - Fundamentals - Dependency injection ~ BỜM TẬP CODE

This series is a collection of knowledge about ASP .NET Core. It just is my notes.

In this note, I want to summary some knowledge about DI in Asp.net core.

First, DI is to archive Inversion of Control, solid principle.

We have 3 types of DI: constructor injection, method injection, property injection

The built-in DI of the .net core base on constructor injection.

a. How to register services

Register a service in method 'ConfigureServices'
Use the "services.Configure" method to config/binding our configuration to option
also can create an extension method of IServicesCollection to compute a group of related service

Note: convention : Add{OurServiceName}, for example: AddDataAcessLayer, AddBusinessServices...

b. Service lifetime

Transient: short lifetime, create when service container request, disposed at the end of the request
Scoped: create per client request, AddDbContext for example.
Singleton: create at the first time that they're requested; disposed of an object only when app shutdown, should consider if we use it, since memory performance

c. Design service for dependency injection

When designing services for dependency injection:

Avoid stateful, static classes and members. Avoid creating a global state by designing apps to use singleton services instead.
Avoid use Service Locator anti-pattern.
Avoid direct instantiation of dependent classes within services. Direct instantiation couples the code to a particular implementation.
Make services small, well-factored, and easily tested.

d. Dispose of services: Container takes this responsibility

e. Keyed Service (From ASP.NET Core 8)

When using keyed services:

Have an interface with multiple implementations
And need to use one of those implementations in different places in your application

Add services by using: AddKeyedSingleton (or AddKeyedScoped or AddKeyedTransient)

builder.Services.AddKeyedSingleton<ICache, BigCache>("big");

builder.Services.AddKeyedSingleton<ICache, SmallCache>("small");

Access a registered service by specifying the key with the [FromKeyedServices]

[HttpGet("big-cache")]

public ActionResult<object> GetOk([FromKeyedServices("big")] ICache cache)

{

return cache.Get("data-mvc");

}

Ref:

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