1.依赖注入的目的是为了解耦。

2.不依赖于具体类，而依赖抽象类或者接口，这叫依赖倒置。

3.控制反转即IoC (Inversion of Control)，它把传统上由程序代码直接操控的对象的调用权交给容器，通过容器来实现对象组件的装配和管理。所谓的“控制反转”概念就是对组件对象控制权的转移，从程序代码本身转移到了外部容器。

4. 微软的DependencyResolver如何创建controller

1、InstancePerDependency

对每一个依赖或每一次调用创建一个新的唯一的实例。这也是默认的创建实例的方式。

官方文档解释：Configure the component so that every dependent component or call to Resolve() gets a new, unique instance (default.)

2、InstancePerLifetimeScope

在一个生命周期域中，每一个依赖或调用创建一个单一的共享的实例，且每一个不同的生命周期域，实例是唯一的，不共享的。

官方文档解释：Configure the component so that every dependent component or call to Resolve() within a single ILifetimeScope gets the same, shared instance. Dependent components in different lifetime scopes will get different instances.

3、InstancePerMatchingLifetimeScope

在一个做标识的生命周期域中，每一个依赖或调用创建一个单一的共享的实例。打了标识了的生命周期域中的子标识域中可以共享父级域中的实例。若在整个继承层次中没有找到打标识的生命周期域，则会抛出异常：DependencyResolutionException。

官方文档解释：Configure the component so that every dependent component or call to Resolve() within a ILifetimeScope tagged with any of the provided tags value gets the same, shared instance. Dependent components in lifetime scopes that are children of the tagged scope will share the parent's instance. If no appropriately tagged scope can be found in the hierarchy an DependencyResolutionException is thrown.

4、InstancePerOwned

在一个生命周期域中所拥有的实例创建的生命周期中，每一个依赖组件或调用Resolve()方法创建一个单一的共享的实例，并且子生命周期域共享父生命周期域中的实例。若在继承层级中没有发现合适的拥有子实例的生命周期域，则抛出异常：DependencyResolutionException。

官方文档解释：Configure the component so that every dependent component or call to Resolve() within a ILifetimeScope created by an owned instance gets the same, shared instance. Dependent components in lifetime scopes that are children of the owned instance scope will share the parent's instance. If no appropriate owned instance scope can be found in the hierarchy an DependencyResolutionException is thrown.

5、SingleInstance

每一次依赖组件或调用Resolve()方法都会得到一个相同的共享的实例。其实就是单例模式。

官方文档解释：Configure the component so that every dependent component or call to Resolve() gets the same, shared instance.

6、InstancePerHttpRequest  （新版autofac建议使用InstancePerRequest）

在一次Http请求上下文中,共享一个组件实例。仅适用于asp.net mvc开发。

官方文档解释：Share one instance of the component within the context of a single HTTP request.

    public class MvcApplication : System.Web.HttpApplication{protected void Application_Start(){AreaRegistration.RegisterAllAreas();FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);RouteConfig.RegisterRoutes(RouteTable.Routes);BundleConfig.RegisterBundles(BundleTable.Bundles);InitDependency();StackExchange.Profiling.EntityFramework6.MiniProfilerEF6.Initialize();}private void InitDependency(){ContainerBuilder builder = new ContainerBuilder();Type baseType = typeof(IDependency);// 自动注册当前程序集//builder.RegisterAssemblyTypes(Assembly.GetExecutingAssembly()).AsImplementedInterfaces();// 注册当前程序集Assembly assemblies = Assembly.GetExecutingAssembly();builder.RegisterAssemblyTypes(assemblies).Where(type => baseType.IsAssignableFrom(type) && !type.IsAbstract).AsImplementedInterfaces().InstancePerLifetimeScope();//保证对象生命周期基于请求//注册引用的程序集//var assemblyList = BuildManager.GetReferencedAssemblies().Cast<Assembly>().Where(assembly => assembly.GetTypes().Any(type => type.GetInterfaces().Contains(baseType)));//var enumerable = assemblyList as Assembly[] ?? assemblyList.ToArray();//if (enumerable.Any())//{//    builder.RegisterAssemblyTypes(enumerable)//        .Where(type => type.GetInterfaces().Contains(baseType))//        .AsImplementedInterfaces().InstancePerLifetimeScope();//}//注册指定的程序集//自动注册了IStudentService、IUserServicebuilder.RegisterAssemblyTypes(Assembly.Load("AppService"), Assembly.Load("AppService")).Where(t => t.Name.EndsWith("Service")).AsImplementedInterfaces();//一、Type注册服务 builder.RegisterType<CourseService>().As<ICourseService>();builder.RegisterType<UserService>().AsSelf();// 注入类本身，等价于.As<UserService>();builder.RegisterType<ScoreManage>().AsImplementedInterfaces();//批量注册，等价于.As<IEnglishScoreManage>().As<IMathematicsScoreManage>();//二、Named注册服务//builder.RegisterType<ChineseScorePlusManage>().Named<IChineseScoreManage>(ChineseScoreEnum.ChineseScorePlus.ToString());// 一个接口与多个类型关联//builder.RegisterType<ChineseScoreManage>().Named<IChineseScoreManage>(ChineseScoreEnum.ChineseScore.ToString());// 一个接口与多个类型关联//三、Keyed注册服务builder.RegisterType<ChineseScorePlusManage>().Keyed<IChineseScoreManage>(ChineseScoreEnum.ChineseScorePlus);// 一个接口与多个类型关联builder.RegisterType<ChineseScoreManage>().Keyed<IChineseScoreManage>(ChineseScoreEnum.ChineseScore);// 一个接口与多个类型关联//泛型注册,可以通过容器返回List<T> 如:List<string>,List<int>等等//builder.RegisterGeneric(typeof(List<>)).As(typeof(IList<>)).InstancePerLifetimeScope();//生命周期//builder.RegisterType<StudentService>().As<IStudentService>().InstancePerLifetimeScope(); //基于线程或者请求的单例..就是一个请求 或者一个线程 共用一个//builder.RegisterType<StudentService>().As<IStudentService>().InstancePerDependency(); //服务对于每次请求都会返回单独的实例//builder.RegisterType<StudentService>().As<IStudentService>().SingleInstance(); //单例.. 整个项目公用一个//builder.RegisterType<StudentService>().As<IStudentService>().InstancePerRequest(); //针对MVC的,或者说是ASP.NET的..每个请求单例
             builder.RegisterType<ServiceGetter>().As<IServiceGetter>();//用于一个接口与多个类型关联
builder.RegisterControllers(Assembly.GetExecutingAssembly()).PropertiesAutowired();//属性注入,未注册将出现“没有为该对象定义无参数的构造函数。”
             builder.RegisterType<TestDbContext>().As<IDbContext>().InstancePerLifetimeScope();builder.RegisterGeneric(typeof(EfRepository<>)).As(typeof(IRepository<>)).InstancePerLifetimeScope();//泛型注入//builder.RegisterFilterProvider(); //注入特性,特性里面要用到相关的服务IContainer container = builder.Build();DependencyResolver.SetResolver(new AutofacDependencyResolver(container));//生成容器并提供给MVC
        }protected void Application_BeginRequest(){if (Request.IsLocal)//这里是允许本地访问启动监控,可不写
            {MiniProfiler.Start();}}protected void Application_EndRequest(){MiniProfiler.Stop();}}

public class HomeController : Controller{private readonly IStudentService _studentService;private readonly ITeacherService _teacherService;private readonly IUserService _userService;public readonly UserService UserService;private readonly IEnglishScoreManage _englishScoreManage;private readonly IMathematicsScoreManage _mathematicsScoreManage;private IServiceGetter getter;public ICourseService CourseService { get; set; }private readonly IRepository<Student> _studentRrepository;public HomeController(IStudentService studentService, IUserService userService, ITeacherService teacherService, UserService userService1, IMathematicsScoreManage mathematicsScoreManage, IEnglishScoreManage englishScoreManage, IServiceGetter getter, IRepository<Student> studentRrepository){_studentService = studentService;_userService = userService;_teacherService = teacherService;this.UserService = userService1;_mathematicsScoreManage = mathematicsScoreManage;_englishScoreManage = englishScoreManage;this.getter = getter;_studentRrepository = studentRrepository;}public ActionResult Index(){var name = "";var student = _studentRrepository.GetById("4b900c95-7aac-4ae6-a122-287763856601");if (student != null){name = student.Name;}ViewBag.Name = _teacherService.GetName();ViewBag.UserName1 = _userService.GetName();ViewBag.UserName2 = UserService.GetName();ViewBag.StudentName = _studentService.GetName() + "-" + name;ViewBag.CourseName = CourseService.GetName();ViewBag.EnglishScore = _englishScoreManage.GetEnglishScore();ViewBag.MathematicsScore = _mathematicsScoreManage.GetMathematicsScore();//ViewBag.ChineseScore = getter.GetByName<IChineseScoreManage>(ChineseScoreEnum.ChineseScore.ToString()).GetScore();//ViewBag.ChineseScorePlus = getter.GetByName<IChineseScoreManage>(ChineseScoreEnum.ChineseScorePlus.ToString()).GetScore();
ViewBag.ChineseScore = getter.GetByKey<ChineseScoreEnum, IChineseScoreManage>(ChineseScoreEnum.ChineseScore).GetScore();ViewBag.ChineseScorePlus = getter.GetByKey<ChineseScoreEnum, IChineseScoreManage>(ChineseScoreEnum.ChineseScorePlus).GetScore();return View();}
}

@{ViewBag.Title = "Home Page";
}<div class="jumbotron"><h1>ASP.NET</h1>
</div><div class="row"><div class="col-md-4"><h2>Teacher: @ViewBag.Name </h2><p>CourseName: @ViewBag.CourseName</p><p></p></div><div class="col-md-4"><h2>User</h2><p>接口注入：@ViewBag.UserName1</p><p>类注入：@ViewBag.UserName2</p></div><div class="col-md-4"><h2>Student： @ViewBag.StudentName</h2><p>English:@ViewBag.EnglishScore</p> <p>Math: @ViewBag.MathematicsScore</p> <p>Chinese: @ViewBag.ChineseScore</p> <p>ChinesePlus:@ViewBag.ChineseScorePlus</p> </div>
</div>