How to register services for DI with Unity

Question

I am a little bit stuck on registering services with Unity in a MVC 5/EF6 app (not .net core).
I have a bunch of services that "do work", and they are injected in Controllers and sometimes in other Services.

This is how i've always registered my services, using RegisterSingleton:

private void ConfigureServices(IServiceCollection services, IUnityContainer unityContainer)
        {
            // Services
            unityContainer.RegisterSingleton<IServiceA, ServiceA>();
            unityContainer.RegisterSingleton<IServiceB, ServiceB>();
            unityContainer.RegisterSingleton<IServiceC, ServiceC>();

            unityContainer.RegisterSingleton<DbContext, ApplicationDbContext>();
        }

Now after some reading, i am a bit confused. Is this the right approach or should I register them using RegisterType?
Mostly, what criteria do you use to decide when to use one or the other?

How do you register your services?

Thanks!

Answer 1

A singleton is a application scoped object where every client request uses the same object instance. With that said, it is unusual for all services in a web application to implement a singleton lifetime. Typically, you'll have a mixture of service lifetimes because not all services work the same way.

I recommend reading the Unity scope documentation to understand what Unity lifetime features are available. Then pick the an appropriate lifetime for each of your services.

Class TypeLifetime