Dependency Injection Notes

Service Registration Methods

Method (specify LIFETIME, SERVICE, IMPLEMENTATION)	Automatic Object Disposal	Multiple Implementations	Pass Arguments
services.AddSingleton<IMyDep, MyDep>();	Yes	Yes	No
services.AddSingleton<IMyDep>(sp => new MyDep());	Yes	Yes	Yes
services.AddSingleton<MyDep>();	Yes	No	No
services.AddSingleton<IMyDep>(new MyDep());	No	Yes	Yes
services.AddSingleton(new MyDep());	No	No	Yes

Source: Dependency injection in .NET

Simple Injection in ASP.NET Core

Install these NuGet Packages:

• SimpleInjector (optional - recommended by Simple Injector for the newest, latest release)
• SimpleInjector.Integration.AspNetCore (optional if SimpleInjector.Integration.AspNetCore.Mvc.Core installed)
• SimpleInjector.Integration.AspNetCore.Mvc
• SimpleInjector.Integration.AspNetCore.Mvc.Core
• SimpleInjector.Integration.AspNetCore.Mvc.ViewFeatures (needed for AddViewComponentActivation() extension method)

using SimpleInjector;

var container = new Container();

var builder = WebApplication.CreateBuilder(args);
var services = builder.Services;

services.AddControllersWithViews();

services.AddSimpleInjector(container, options =>
{
   options.AddAspNetCore()
      .AddControllerActivation()
      .AddViewComponentActivation()
      .AddPageModelActivation()
      .AddTagHelperActivation();
   options.AutoCrossWireFrameworkComponents = false;  // default is true
   options.CrossWire<ILogger<HomeController>>();
   options.CrossWire<IMyApplicationService>();
});

container.Register<IDemoService, DemoService>(Lifestyle.Singleton);
services.AddSingleton<IDemoService, CoreDemoService>();  // No error if already registered in Simple Injector
// SimpleInjector will inject SimpleInjector instance if it exists
// Otherwise SimpleInjector will inject the instance from IServiceCollection
// (only if AutoCrossWireFrameworkComponents == true or specified with CrossFire)

var app = builder.Build();

app.Services.UseSimpleInjector(container);

container.Verify();

app.Run();