Automatically register all implementations of a generic interface in service container

I have a generic interface which has many implementations. I expect to have more implementations of this generic interface in the future. However, I don’t want to manually register these implementations in the service container every time I add a new one. It’d also cause runtime exception if I forget to register one of these implementations. In this post, I’m going to show how to automatically register all implementations of a generic interface during start up.

Let’s say the generic interface looks similar to the one below

    public interface IGenericInterface
    {
        bool DoSomething(string someInput);
    }

And it has 2 implementations as followed

    public class ClassA : IGenericInterface<ClassA>
    {
        public bool DoSomething(string someInput)
        {
            // Business logic goes here

            return true;
        }
    }

    public class ClassB : IGenericInterface<ClassB>
    {
        public bool DoSomething(string someInput)
        {
            // Business logic goes here

            return false;
        }
    }

Then, in order to automatically register these implementations, in ConfigureServices method in Startup.cs class, do the following

    public void ConfigureServices(IServiceCollection services)
    {
        // Other service registrations go here

        var assemblyTypes = Assembly.GetAssembly(typeof(Startup)).GetTypes();

        foreach (var genericType in assemblyTypes.Where(x => !x.IsInterface &&
                                           x.GetInterfaces().Any(i => i.IsGenericType &&
                                                                      typeof(IGenericInterface<>).IsAssignableFrom(i.GetGenericTypeDefinition()))))
        {
            services.AddTransient(genericType.GetInterfaces().First(), genericType);
        }
    }