How to inject dependencies of generics in ASP.NET Core

I know this is very late but I am posting my solution here so that others can refer and use this. I have written some extensions to register all the derived types of generic interface.

public static List<TypeInfo> GetTypesAssignableTo(this Assembly assembly, Type compareType)
{
        var typeInfoList = assembly.DefinedTypes.Where(x => x.IsClass 
                            && !x.IsAbstract 
                            && x != compareType
                            && x.GetInterfaces()
                                    .Any(i => i.IsGenericType
                                            && i.GetGenericTypeDefinition() == compareType))?.ToList();

        return typeInfoList;
 }

public static void AddClassesAsImplementedInterface(
        this IServiceCollection services, 
        Assembly assembly, 
        Type compareType,
        ServiceLifetime lifetime = ServiceLifetime.Scoped)
 {
        assembly.GetTypesAssignableTo(compareType).ForEach((type) =>
        {
            foreach (var implementedInterface in type.ImplementedInterfaces)
            {
                switch (lifetime)
                {
                    case ServiceLifetime.Scoped:
                        services.AddScoped(implementedInterface, type);
                        break;
                    case ServiceLifetime.Singleton:
                        services.AddSingleton(implementedInterface, type);
                        break;
                    case ServiceLifetime.Transient:
                        services.AddTransient(implementedInterface, type);
                        break;
                }
            }
        });
}

In the startup class, you just register your generic interface like below.

services.AddClassesAsImplementedInterface(Assembly.GetEntryAssembly(), typeof(IRepository<>));

You can find the complete extension code in this Github repository.

Repository<T> is an abstract class, so you cannot register it as an implementation, because abstract class simply cannot be instantiated. Your registration would work fine if Repository<T> was not abstract.

If you cannot make repository class non-abstract, you can register specific implementation of your repository class:

services.AddScoped(typeof(IRepository<Test>), typeof(TestRepository));

This will correctly inject dependencies to your controller.