What is service lifetimes in ASP.NET Core?

ASP.net core allows us to specify the lifetime for registered services. The service instance gets disposed of automatically based on a specified life-time. So we do not care about the cleaning these dependencies, it will take care of the ASP.net core framework. There are three types of life-times.
1 - Transient
2 - Scoped
3 - Singleton

For more details check the below links.
https://www.dotnettricks.com/learn/dependencyinjection/implementation-asp-net-core-mvc
https://code-maze.com/dependency-injection-lifetimes-aspnet-core/

There are three lifetimes that can be used with Microsoft Dependency Injection Container, they are:

 

• Transient — Services are created each time they are requested. It gets a new instance of the injected object, on each request of this object. For each time you inject this object is injected in the class, it will create a new instance.

 

• Scoped — Services are created on each request (once per request). This is most recommended for WEB applications. So for example, if during a request you use the same dependency injection, in many places, you will use the same instance of that object, it will make reference to the same memory allocation.

 

• Singleton — Services are created once for the lifetime of the application. It uses the same instance for the whole application

Service lifetimes available in .NET Core:

• Transient – created each time they’re requested from the service container
• Scoped – created once per client request and is reused within that request
• Singleton – created only once and is reused across the application’s lifetime

We can register these services with the AddTransient(), AddScoped() and AddSingleton() methods respectively.

They are services, which will be used and integrated using depedency injection, There are 3 types of lifetimes supported by ASP.NET Core for the dependency injection,They are,

1)Transient Service

2)Scoped Service

3)Singleton Service

 

https://www.c-sharpcorner.com/article/service-lifetime-dependency-injection-asp-net-core/