首先我在global.ascx中，在应用程序启动之前添加了如下代码，调用了Application_start 进行了依赖注入

namespace MVC3.Extensions
{
    public class Application_Start
    {
        public static void Run()
        {
            var builder = new ContainerBuilder();
            var data = Assembly.Load("Service");
            builder.RegisterAssemblyTypes(data)
                  .Where(a=>a.FullName.Contains("SqlServer")).AsImplementedInterfaces();
            builder.RegisterControllers(Assembly.GetExecutingAssembly());
            var container = builder.Build();
            DependencyResolver.SetResolver(new AutofacDependencyResolver(container));
        }
    }
}

在我的项目中有IService，Service，Models这三个类库，但是我今天阅读别人的代码，发现在网站启动的HomeController的构造函数中存在

 public class HomeController : Controller
    {
        private readonly INewsService _newsService;
        //
        // GET: /Home/
        private const string picturePath = "~/xml/pictureRoll.xml";
        public ActionResult Index()
        {
            List<News> list = _newsService.GetAll();
            return View(list);
        }

        public HomeController(INewsService newsService)
        {
            this._newsService = newsService;
        }

        public ActionResult PictureRoll()
        {
            System.Text.StringBuilder picture = new System.Text.StringBuilder();
            XElement xe = XElement.Load(Server.MapPath(picturePath));
            var query = from value in xe.Elements("img")
                        select value;
            foreach (var item in query)
            {
                picture.Append(string.Format("<img src=\"/File/ScrollImage/{0}\"  title=\"{1}\"  alt=\"{1}\"/>",item.Element("path").Value,item.Element("title").Value));
            }
            ViewBag.PictureScroll = picture.ToString();
            return View();
        }

    }

我现在就想知道，这个构造函数中的参数是如何传递到homeController的