Question

I have the classes below:

SuppliersRepository.cs (with the interface defining the method):

    public class SuppliersRepository : BaseRepository,ISuppliersRepository
    {
        public IEnumerable<Supplier> GetSuppliersByCoordinates(double latitude, double longitude)
        {
            using (IDbConnection connection = OpenConnection())
            {
                const string query = "SELECT ID=SupplierID,Name=Suppliername FROM suppliers WHERE dbo.Distance(@latitude,@longitude,latitude,longitude) < 15 AND latitude IS NOT NULL AND longitude IS NOT NULL";
                return connection.Query<Supplier>(query, new { latitude = latitude,longitude=longitude });
            }
        }

    }

BaseRepository.cs (with the interface defining the method)

public abstract class BaseRepository: IBaseRepository
{
    public IDbConnection OpenConnection()
    {
        IDbConnection connection = new SqlConnection(WebConfigurationManager.ConnectionStrings["myconnection"].ConnectionString);
        connection.Open();
        return connection;
    }

}

A Bootstraper.cs called from global.asax.cs with:

public static class Bootstrapper
    {
        public static void Initialise()
        {
            var container = BuildUnityContainer();

            DependencyResolver.SetResolver(new UnityDependencyResolver(container));
        }

        private static IUnityContainer BuildUnityContainer()
        {
            var container = new UnityContainer();

            container.RegisterType<IBaseRepository, BaseRepository>();
            container.RegisterType<ISuppliersRepository, SuppliersRepository>();
            container.RegisterInstance<IHttpControllerActivator>(new HttpControllerActivator(container));
            container.RegisterControllers();


            return container;
        }
    }

And two controllers, first one resolves the repository fine:

public class VenueController : MasterController
    {
        [Dependency]
        public SuppliersRepository _SuppliersRepository { get; set; }
    }

But this one fails:

public class AjaxController : Controller
    {
        [Dependency]
        public BaseRepository _BaseRepository { get; set; }
}

It throws a System.InvalidOperationException: The type BaseRepository cannot be constructed. You must configure the container to supply this value.

Any idea what am I doing wrong?

Answer 1

First of all, when using dependency injection, it’s better to have dependencies on interfaces, rather than having dependencies on concrete classes. I would change your controllers to

public class VenueController : MasterController
{
    [Dependency]
    public ISuppliersRepository _SuppliersRepository { get; set; }
}


public class AjaxController : Controller
{
    [Dependency]
    public IBaseRepository _BaseRepository { get; set; }
}

Second, BaseRepository is abstract class. Instances of abstract class can not be constructed, and I think that’s the reason why it fails when unity comes to actually creating BaseRepository. You should inject concrete classes.

container.RegisterType<IBaseRepository, SomeConcreteImplementationOfBaseRepository>();