How to inject dependencies of generics in ASP.NET Core

Question

I have following repository classes:

public class TestRepository : Repository<Test>
{
    private TestContext _context;

    public TestRepository(TestContext context) : base(context)
    {
        _context = context;
    }
}

public abstract class Repository<T> : IRepository<T> where T : Entity
{
    private TestContext _context;

    public Repository(TestContext context)
    {
        _context = context;
    }
    ...
}

public interface IRepository<T>    
{
    ...
}

How do I implement the dependency injection in ASP.NET Core in my Startup.cs?

I implemented it like this:

services.AddScoped(typeof(IRepository<>), typeof(Repository<>));

But then I get following error:

Cannot instantiate implementation type 'Test.Domain.Repository1[T]' for service type 'Test.Domain.IRepository1[T]'.

Answer 1

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.