.Net Core WebApi Dependency Injection - asp.net-core

Question

I have a solution and I have different projects in it.
One of them is the api project and I want to use dependency injection in this project, but I get the following error:
Some services are not able to be constructed (Error while validating the service descriptor 'ServiceType: CCM.Business.Abstract.ICompanyService Lifetime: Scoped ImplementationType: CCM.Business.Concrete.CompanyManager': Unable to resolve service for type 'CCM.DataAccess.Concrete.CompanyDal' while attempting to activate 'CCM.Business.Concrete.CompanyManager'.)
Startup.cs:
public void ConfigureServices(IServiceCollection services)
{
services.AddControllers();
services.AddScoped<ICompanyDal, CompanyDal>();
services.AddScoped<ICompanyService, CompanyManager>();
}
ICompanyDal:
public interface ICompanyDal: IGenericDal<Company>
{
}
CompanyDal:
public class CompanyDal:GenericDal<Company,CCMContext>,ICompanyDal
{
}
ICompanyService:
public interface ICompanyService
{
Company GetById(int id);
List<Company> GetAll();
void Create(Company entity);
void Update(Company entity);
void Delete(Company entity);
}
CompanyManager:
public class CompanyManager : ICompanyService
{
private CompanyDal _companyDal;
public CompanyManager(CompanyDal companyDal)
{
_companyDal = companyDal;
}
public void Create(Company entity)
{
_companyDal.Create(entity);
}
public void Delete(Company entity)
{
_companyDal.Delete(entity);
}
public List<Company> GetAll()
{
return _companyDal.GetAll();
}
public Company GetById(int id)
{
return _companyDal.GetById(id);
}
public void Update(Company entity)
{
_companyDal.Update(entity);
}
}
Is there anything else I should pass on to you? please help.

Answer 1

In startup, you add the service ICompanyDal with the implementation CompanyDal. But in CompanyManager, you inject the implementation CompanyDal, not the service ICompanyDal.
Solution, inject the service in the constructor :
public class CompanyManager : ICompanyService
{
private ICompanyDal _companyDal;
public CompanyManager(ICompanyDal companyDal)
{
_companyDal = companyDal;
}
...

Answer 2

Change the CompanyManager to explicitly depend on the registered abstraction
CompanyManager:
//...
private ICompanyDal _companyDal;
//CTOR
public CompanyManager(ICompanyDal companyDal) {
_companyDal = companyDal;
}
//...
since that is what was registered with the container
Startup:
//...
services.AddScoped<ICompanyDal, CompanyDal>();
//...
Make sure that your controller(s) follow a similar format and explicitly depends on the registered abstraction(s) as well
Controller:
//...
public MyController(ICompanyService service) {
//...
}
//...