具有通用服务和存储库的Autofac

Question

I'am facing an issue with the architecture set in place while trying to use Autofac.

Error message encountered is the following:

None of the constructors found with 'Autofac.Core.Activators.Reflection.DefaultConstructorFinder' on type 'xx.xx.xxxxxxx.HomeController' can be invoked with the available services and parameters: Cannot resolve parameter 'xx.Service.Common.IGenericService 2[xx.Common.Models.EntCountry,System.Int32] countryService' of constructor 'Void .ctor(xx.Service.Common.IGenericService 2[xx.Common.Models.EntCountry,System.Int32])'.

Repository Interface and Class

 public interface IGenericRepository<T,TId> 
        where T: class , IEntity<TId>
    {...}

 public abstract class GenericRepository<T, TId> : IGenericRepository<T, TId>  
        where T : class, IEntity<TId>
        where TId : class {}

Service Interface and Class

 public interface IGenericService<T,TId> where T : class , IEntity<TId> 
    {...}



public abstract class GenericService<T, TId> : IGenericService<T, TId>  
        where T : class, IEntity<TId> 
        where TId : class{...}

Controller Code

   public class HomeController : Controller
    {

    private readonly IGenericService<EntCountry, int> _countryService;

    public HomeController(IGenericService<EntCountry, int> countryService)
    {
        _countryService = countryService;
    }

    // GET: Home
    public ActionResult Index()
    {

        var countries = _countryService.GetAll();

        return View();
    }
}

My Autofac configuration for services and repository is the following:

builder.RegisterAssemblyTypes(Assembly.Load("XX.Data"))
                   .Where(t => t.Name.EndsWith("Repository"))
                   .AsImplementedInterfaces()
                   .AsSelf()
     .PropertiesAutowired(PropertyWiringOptions.AllowCircularDependencies)
                   .InstancePerLifetimeScope();





 builder.RegisterAssemblyTypes(Assembly.Load("XX.Service"))
                   .Where(t => t.Name.EndsWith("Service"))
                   .AsImplementedInterfaces()
                   .AsSelf()
                   .PropertiesAutowired(PropertyWiringOptions.AllowCircularDependencies)
                   .InstancePerLifetimeScope();

I tried to use the Register Generic method, but I still got the same error

builder.RegisterGeneric(typeof(GenericRepository<,>))
                .As(typeof(IGenericRepository<,>))
                .AsSelf()
                .InstancePerDependency();

Thanks for your help.

best regards.

Answer 1

The error message indicates that IGenericService<EntCountry, Int32> is not registered.

Because GenericService is abstract the first solution would be to have an implementation of such a class

public class FooService : GenericService<Foo, Int32> 
{ }

Then Autofac will register FooService as IGenericService<Foo, Int32>

If you don't want to have an implementation but only use GenericService<T, TId> you will have to remove the abstract modifier and change how you register your type in Autofac .

Unfortunately there is no easy way to register an open generic type when scanning assemblies. There is an active open issue about this in Autofac Github : Support registering open generic types when scanning assemblies

The easiest solution is to register this type manually

builder.RegisterGeneric(typeof(GenericService<,>))
       .AsImplementedInterfaces();

If it is not possible have a look at the Github issue there is some solution you could play with.

---

There will also be another issue with the code provided. The IGenericService<T, TId> has a class constraint ( where TId : class ) but in the exception TId is a Int32 wich is not valid for the .net runtime. You should remove the class constraint or change the type of TId .