Example of collecting API endpoints. Considering how to get type from assembly in line assembly.GetTypes()...

EndpointExtensions.cs

public static class EndpointExtensions
{
    public static IServiceCollection AddEndpoints(this IServiceCollection services, Assembly assembly)
    {
        var types = assembly
            .GetTypes()
            .Where(
                t =>
                t is { IsInterface: false, IsAbstract: false } &&
                typeof(IEndpoint).IsAssignableFrom(t)
            )
            .Select(t => new ServiceDescriptor(typeof(IEndpoint), t, ServiceLifetime.Transient))
            .ToList();

        services.TryAdd(types);

        return services;
    }

    public static IApplicationBuilder MapEndpoints(this IApplicationBuilder app, IEndpointRouteBuilder routeBuilder)
    {
        var endpoints = app.ApplicationServices.GetRequiredService<IEnumerable<IEndpoint>>();

        foreach (var endpoint in endpoints)
        {
            var endpointTypeName = endpoint.GetType().Name;
            var routePrefix = endpointTypeName[..^"Endpoint".Length];

            endpoint.MapEndpoint(routeBuilder, routePrefix);
        }

        return app;
    }
}