How to select the lifetime scope for dependencies

Question

Hi,
I am following the example in the link below,

https://github.com/microsoftgraph/msgraph-training-changenotifications/blob/master/demos/03-track-changes/Controllers/NotificationsController.cs

If I move the methods in it to separate service classes, what should be the scope while registering services in Startup.cs

For example if I move the Graph related methods(GetGraphClient(),GetAccessToken() etc) to GraphService and create an interface IGraphService , how should I register it in startup? Soped?transient?singleton?

Thanks

Answer 1

It's important to understand the lifetime of the services when you are doing the DI, so you can choose what's best.

• services.AddTransient:<>
  • Transient objects are always different. That's a new object is created every time it's requested.
• services.AddScoped<>
  • Scoped objects are the same for a given request but differ across each new request.
• services.AddSingleton<>
  • Singleton objects are the same for every request.

I believe this will help you determine what's best for your scenario.

Answer 2

The documentation is very clear and states, "Singleton objects are the same for every request." It does not matter what device, user (browser), client makes the request, the Singleton is the same instance for every request.

Dependency Injection: Lifetime and registration options

I believe scoped dependency is alive for the session of the user.

No. Scoped life time is the duration of a request. A new request gets a new scope. From the docs... "Scoped objects are the same for a given request but differ across each new request."

Is there any convention that service class should be scoped, repository class should be singleton etc?

It depends on the repository design.