public static class AutofacExt
    {
        static ContainerBuilder containerBuilder;
        static IContainer _container;
        public static IContainer container
        {
            get
            {
                if (_container == null)
                {
                    _container = containerBuilder.Build();
                }
                return _container;
            }
        }
        public static void InitAutofact()
        {
            containerBuilder = new ContainerBuilder();

            var config = new ConfigurationBuilder();
            config.AddXmlFile("Autofac.config");

            var module = new ConfigurationModule(config.Build());
            
            containerBuilder.RegisterModule(module);

            _container = containerBuilder.Build();
        }
        public static T GetObject<T>()
        {
            return container.Resolve<T>();
        }

    }

<?xml version="1.0" encoding="utf-8" ?>

<configuration>
  
  <configSections>
    <section name="Default" type="Autofac.Configuration.SectionHandler, Autofac.Configuration"/>
  </configSections>
  <Default>
    <components>
      <componet type="ImplementBLL.CustomersBLL,ImplementBLL" service="InterfaceBLL.ICustomersBLL,InterfaceBLL" />
    </components>
  </Default>
 
</configuration>

 public ActionResult Index()
        {
            AutofacExt.InitAutofact();
            var cusBLL = AutofacExt.GetObject<ICustomersBLL>();
            var customers = cusBLL.GetCustomers();

            return View(customers);
        }