.NET supports the dependency injection (DI) software design pattern, which is a technique for achieving Inversion of Control (IoC) between classes and their dependencies.

All these dependencies are registered inside the Startup.cs within ConfigureServices method of our application and must have a specific lifetime.

Service Lifetimes

Services can be registered with one of the following available lifetimes:

• Transient
• Scoped
• Singleton

Transient Scope

When a service is been registered as transient it means a new instance of the service is created, every time you request it. To register a service as transient use the AddTransient extension method. For example.

public void ConfigureServices(IServiceCollection services)
{
    services.AddTransient<IMyTransientService, MyTransientService>();
}

Scoped Scope

When a service is registered as scoped, a new instance of the service is been created for each scope/request. Within the scope the existing instance of the service is used. To register a service as scoped use the AddScoped extension method as shown in the following code snippet.

public void ConfigureServices(IServiceCollection services)
{
    services.AddScoped<IMyScopedService, MyScopedService>();
}

Singleton Scope

When a service is registered as singleton it means that only one instance of that service is been created during the application lifetime. To register a service as singleton use the AddSingleton extension method as shown in the following code snippet.

public void ConfigureServices(IServiceCollection services)
{
    services.AddScoped<IMySingletonService, MySingletonService>();
}