ASP.NET MultiLayer App Migration To ASP.NET Core

Question

I migrate my ASP.NET multi layer project to ASP.NET Core. I was using Ninject for DI in my old project and i could call it as follow in my BLL.

public void  IamMethodInBll()
{
    ...
    //i could call ninject like this.
    var prodCalcManager = Const.NinjectKernel.Get<IProdCalcService>();
    prodSurr.CalculatedPrice = prodCalcManager.GetMyMethod()
    ..
}

In now i use ASP Net Core's DI system of course. But how can i call the service locator in business layer for ASP.NET core? I need your samples and suggestions.

In Startup.cs

services.AddScoped<IProdCalcService,ProdCalcManager>();

In BLL

public void  IamMethodInBll()
{
    ...
    //What's the proper way to call another service in BLL
    //How can  i get the service provider in BLL
    var prodCalcManager = _serviceProvider.GetService<IProdCalcService>();
    prodSurr.CalculatedPrice = prodCalcManager.GetMyMethod()
    ..
}

Use explicit dependency principle via constructor injection. Try to avoid using service locator anti-pattern. — Nkosi, Jun 12 '19 at 11:50
[Here's an article](https://freecontent.manning.com/dependency-injection-in-net-2nd-edition-understanding-the-composition-root/) that describes the problems with Service Locator in more detail. — Steven, Jun 13 '19 at 11:36

Robert Perry · Accepted Answer · 2019-06-12T13:32:58.377

The correct answer is: Dont use ServiceLocator. Register your services using the services.AddScoped<T> like you are and then add that to the constructor of the class you want to use it in.

Like so:

services.AddScoped<IProdCalcService,ProdCalcManager>();

Then your class looks like this:

public class MyClass()
{

    private IProdCalcService calcService;

    public MyClass(IProdCalcService calcService)
    {
        this.calcService = calcService;
    }

    public void IamMethodInBll()
    {

        //...

        prodSurr.CalculatedPrice = calcService.GetMyMethod();

        //...
    }
}

Saeid Babaei · Answer 2 · 2019-06-12T12:54:35.973

It is better to DONT USE Service Locator but in this case you can inject ServiceProvider to your Controller or better solution is wrap and abstract ServiceProvider in a Container that can be injectable simply. I prefer to use 3rd party DI Containers for use in this situation, specially CastleCore can be good choice.

public interface IContainer 
{
   T Resolve<T>();
}

public class ServiceProviderContainer : IContainer 
{
  private IServiceProvider _serviceProvider; 
  public ServiceProviderContainer(IServiceProvider serviceProvider)
  {
    this._serivceProvider = serviceProvider;
  }

  public T Resolve<T>()
  {
     return _seriveProvider.GetService<T>();
  }
}


public class MyController : Controller 
{ 
  private IContainer contianer;
  public MyController(IContainer container)
  {
    this._container = container;
  }

  public IActionResult Get()
  {
    var service = _container.Resolve<IUserRepository>();
  }
}

How-to ***inject*** `ServiceProvider` in a **BLL class**, for example, NOT Controller? — Kiquenet, Aug 30 '22 at 10:43
Just like the code sample I provide, You need only inject IContainer to your XXXService or XXXManager in BLL layer — Saeid Babaei, Sep 01 '22 at 20:15

ASP.NET MultiLayer App Migration To ASP.NET Core

2 Answers2