Services

What is it?

Services in ASP.NET, are basically classes that can be easily reused in different locations, without having to worry about instantiating them in their dependence. For example, the class that’s responsible for connecting to databases is a service.

---

Creating services

Any class that implements an interface can act as a service. Let’s create a example:

public interface IService
{
	string Method();
}
 
public class MyService: IService
{
	public string Method()
	{
		return "Returning value";
	}
}

The code above is not yet a service. To make it a service, it needs to be registered as service, before building the application. There’re three main ways to register services:

• Singleton

  Used when only one instance of the service will be ran for the application entire lifetime. All requests will go through the same instance of the service.

• Scoped

  Each scope will create its own single instance of the service. Each request creates its own instance, per scope.

• Transient

  Every request will create a different instance, every time it’s requested.

Let’s register the created service as a singleton:

// Before building the application
builder.Services.AddSingleton<IService, MyService>();
 
// var app = builder.Build();

Now, the service is registered to the Dependency Injection container. Now Dependency Injection will manage and distribute the service as needed.

---

Using the service

One can access different services in various parts of the application using Dependency Injection, injecting it in a middleware component.