ASP.NET Core Dependency Injection 3

Question 1

Which lifetime should be used for a service that maintains shared state across all requests?

Accepted Answer

Singleton

Answer

Singleton services are instantiated once for the application lifetime, making them appropriate for shared, thread-safe state.

Question 2

What is the default DI container used in ASP.NET Core?

Accepted Answer

Microsoft.Extensions.DependencyInjection

Answer

ASP.NET Core ships with its own lightweight DI container in the Microsoft.Extensions.DependencyInjection package.

Question 3

How is scope validation enabled in ASP.NET Core DI to detect captive dependencies?

Accepted Answer

Set ValidateScopes = true in ServiceProviderOptions

Answer

Setting ValidateScopes = true (default in Development) causes the container to throw when a captive dependency is detected.

Question 4

Which method lets you replace an existing service registration in ASP.NET Core DI?

Accepted Answer

services.Replace(ServiceDescriptor.Scoped<IService, NewImpl>())

Answer

services.Replace() removes the existing descriptor for the service type and adds the new one.

Question 5

What happens if a service is not registered and GetService<T>() is called?

Accepted Answer

It returns null

Answer

Unlike GetRequiredService, GetService<T>() returns null when the service type is not registered.

ASP.NET Core Practice Test