'Some services are not able to be constructed (Error while validating the service descriptor 'ServiceType:

Question

I'm creating an application in .net 7, using dapper in the layers pattern, Apresetation, Application, Domain, Infra

.net 7 doesn't have startup.cs to do the injections, I'm doing them in program.cs.

when my service (Application) calls my Domain, the injection error occurs, but it has been done.

Program.cs

using Ecommerce.Application.Services;
using Ecommerce.Application.Services.Interfaces;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddControllers();  
// Add services to the container.
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

builder.Services.AddScoped<IFazerPedidoService, FazerPedidoService>();
//builder.Services.AddScoped<IFazerPedidoDomainService, FazerPedidoDomainService>();

var app = builder.Build();
// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.Run();

Sevice

 public class FazerPedidoService : IFazerPedidoService
 {
     private readonly IFazerPedidoDomainService _fazerPedidoDomainService;
     public FazerPedidoService()
     {
     }

     public FazerPedidoModel FazerPedido(FazerPedidoModel fazerPedidoModel)
     {
         var pedido = new FazerPedidoEntity
         {
             Id = 999
         };

         pedido = _fazerPedidoDomainService.FazerPedidoDomain(pedido);
         return fazerPedidoModel;
     }
 }

namespace Ecommerce.Domain.Interfaces
{
    public interface IFazerPedidoDomainService
    {
        public FazerPedidoEntity FazerPedidoDomain(FazerPedidoEntity fazerPedidoEntity);
    }
}

I need to make this call

Answer 1

Well no, they are not OK.

As I mentioned, you must ensure that you inject all of your services, at any level, not just the top level one.

Instead of

builder.Services.AddSingleton<IFazerPedidoService, FazerPedidoService>();

Do this:

builder.Services.AddSingleton<IFazerPedidoService, FazerPedidoService>();
builder.Services.AddSingleton<IFazerPedidoDomainService, FazerPedidoDomainService>();
// Assuming you have FazerPedidoRepository class here
builder.Services.AddSingleton<IFazerPedidoRepository, FazerPedidoRepository >();

(And change them back to AddScoped(), it should work perfectly fine)

---

Explanation:

Look at how you are injecting the IFazerPedidoService. There are 2 steps:

1. Register the dependency in the Program.cs
2. Pass it via the constructor to the caller interface (in your case it's a controller).

You need to follow the same pattern for any other service you have, regardless of where you are consuming it (i.e. controller or other injected service).

In your case C# DI (dependency injection) has no clue how to 'enable' the IFazerPedidoService, because it cannot recognize the IFazerPedidoDomainService, which cannot recognize the IFazerPedidoRepository . Do you see the pattern?

Inject all the way down, all the necessary services and it will work.