Problem Registering services for DI in NET CORE 3

Question

I am applying dependency injection to my dotnet 3.1 project. I created a class ServiceRegister in my Application layer:

namespace Microsoft.Extensions.DependencyInjection
{
    public static class ServiceRegister
    {
        public static IServiceCollection AddApplicationServices(this IServiceCollection @this)
        {
            // Cart Services
            @this.AddTransient<AddCustomerInformation>();
            @this.AddTransient<AddToCart>();
            @this.AddTransient<GetCart>();
            @this.AddTransient<GetCustomerInformation>();
            @this.AddTransient<Application.Cart.GetOrder>();

            // Orders Services
            @this.AddTransient<CreateOrder>();
            @this.AddTransient<Application.Orders.GetOrder>();

            // Orders Admin Services
            @this.AddTransient<Application.OrdersAdmin.GetOrder>();
            @this.AddTransient<GetOrders>();
            @this.AddTransient<UpdateOrder>();

            // Products Services
            @this.AddTransient<Application.Products.GetProduct>();
            @this.AddTransient<GetProducts>();

            // Products Admin Services
            @this.AddTransient<CreateProduct>();
            @this.AddTransient<DeleteProduct>();
            @this.AddTransient<GetProduct>();
            @this.AddTransient<UpdateProduct>();

            // Stock Admin Services
            @this.AddTransient<CreateStock>();
            @this.AddTransient<DeleteStock>();
            @this.AddTransient<GetStock>();
            @this.AddTransient<UpdateStock>();

            // Users Admin Services
            @this.AddTransient<CreateUser>();

            return @this;
        }
    }
}

In my startup class I added:

services.AddApplicationServices();

When I run the app, the program errors with the following:

ArgumentException: Cannot instantiate implementation type 'Microsoft.AspNetCore.Http.ISession' for service type 'Microsoft.AspNetCore.Http.ISession'

In my addCustomerInformation class I have this constructor:

public class AddCustomerInformation
{
    private readonly ISession _session;

    public AddCustomerInformation(ISession session)
    {
        _session = session;
    }
}

I am not an expert in DI, I'm assuming that I also need to register ISession somehow in my serviceRegister class, not sure how should I do that, any clues?? I tried to add this in the register:

this.AddScoped();

But no luck either, it throws an error saying that Session cannot be found, and thats after adding a reference to Microsoft.AspNetCore.Http. I'm sure I'm missing something just can't figure it out.

Answer 1

You should register the dependencies like this:

services.AddScoped<IInterface, Implemantation>();

You need to specify the interface to which you register a specific implementation . You can review the documantation for more details.

After that you inject the interface like this:

public class Service
{
    private readonly IInterface _interface;
    public Service(IInterface interface)
    {
        _interface = interface;
    }
}