autofac对比工厂有哪些优点？

对比下来没感觉到 autofac 有哪些优势

///使用 autofac 
ContainerBuilder builder = new ContainerBuilder();
builder.RegisterType<DBLog>().As<ILog>();
builder.RegisterType<ProductService>();
var container = builder.Build();
var productService = container.Resolve<ProductService>();


///使用工厂模式
var pro = new ProductServiceNotAutofac(LogFac.GetLog());

两种方式一样可以达到目的，为什么会有autofac



    public interface ILog
    {
        void SaveLog(string message);
    }


    public class DBLog : ILog
    {
        public DBLog()
        {
            Console.Write("is DBLog");
        }

        public void SaveLog(string message)
        {
            // save log here.

            Console.WriteLine("DBLog here" + message);
        }
    }

    public class TextLog : ILog
    {

        public TextLog()
        {
            Console.Write("is TextLog");
        }

        public void SaveLog(string message)
        {
            // save log here.

            Console.WriteLine("TextLog here" + message);
        }

    }




    public class ProductService
    {
        private ILog _log;
        public ProductService(ILog log)
        {
            _log = log;
            _log.SaveLog(" hi ");
        }
    }



    public class ProductServiceNotAutofac
    {
        private ILog _log;
        public ProductServiceNotAutofac(ILog log)
        {
            _log = log;
            _log.SaveLog(" hi ");
        }
    }


    /// <summary>
    /// log工厂
    /// </summary>
    public static class LogFac
    {
        public static ILog GetLog()
        {
            string logk = "";

            switch (logk)
            {
                case "dblog":
                    return new DBLog();
                    break;

                case "textlog":
                default:
                    return new TextLog();
                    break;
            }
        }
    }


    class Program
    {
        static void Main(string[] args)
        {

            ///使用 autofac 
            ContainerBuilder builder = new ContainerBuilder();
            builder.RegisterType<DBLog>().As<ILog>();
            builder.RegisterType<ProductService>();


            var container = builder.Build();
            var productService = container.Resolve<ProductService>();


        


            ///使用工厂
            var pro = new ProductServiceNotAutofac(LogFac.GetLog());

            Console.Read();

        }
    }