Dependency Injection in NetCore

Dependency Injection [DI] is a pattern that gives the implementation of a class to an object without needing a Factory or the object knowing how to instantiate it with the intent to decoupling these objects.

We are going to describe the purposes of the three types of patterns available in NetCore: “Singleton”, “Scoped” and “Transient”.

The purpose of Singleton is to instantiate your object only once and then whenever you need that object, you will use the same implementation. This is useful for example for caching.

Then, we have Scoped. When it is applied your object will be instantiated once per request lifecycle. This is useful for example for Repositories or Services.

Lastly, we have Transient. This is the most common of the three because it is going to be instantiated whenever it is invoked.

In NetCore you define your DI inside Startup.cs on ConfigureServices method. Now, let’s see how you can define this.

Singleton:

services.AddSingleton<Interface, ImplementationClass>();

Scoped:

services.AddScoped<Interface, ImplementationClass>();

Transient:

services.AddTransient<Interface, ImplementationClass>();

You can read more about this pattern on:

https://martinfowler.com/articles/injection.html

If you have any doubt don’t hesitate to leave your comments or asking me ​​via Twitter.