IoC在Web API中的应用

控制反转（Inversion of Control，英文缩写为IoC）是框架的重要特征，并非面向对象编程的专用术语。它与依赖注入（Dependency Injection，简称DI）和依赖查找

（Dependency Lookup）并没有关系。简单地说，就是应用本身不负责依赖对象的创建和维护，而交给一个外部容器来负责。这样控制权就由应用转移到了外部IoC容器，

控制权就实现了所谓的反转。

一、引用Unity

将IoC应用于HttpController激活系统的目的在于让一个预定义的IoC容器来提供最终的HttpController对象

引用NuGet包的Unity

然后在 Web API应用中定义了这个UnityHttpControllerActivator类型。UnityHttpControllerActivator具有一个表示Unity容器的属性UnityContainer，该属性在构造函数

中被初始化。在用于创建的HttpController的Create方法中，我们调用此UnityContainer对象的Resolve方法创建目标HttpController对象。

  public class UnityHttpControllerActivator :IHttpControllerActivator
    {
        public IUnityContainer UnityContainer { get; private set; }

        public UnityHttpControllerActivator(IUnityContainer unityContainer)
        {
            this.UnityContainer = unityContainer;
        }

        public IHttpController Create(HttpRequestMessage request, HttpControllerDescriptor controllerDescriptor, Type controllerType)
        {
            return (IHttpController)this.UnityContainer.Resolve(controllerType);
        }
    }

接下来我们定义了如下一个继承自ApiController的UserController来简单起见

 [RoutePrefix("api/WeChat")]
    public class UserController : ApiController
    {

        public IUserRepository IUser { get; private set; }

        public UserController(IUserRepository IUser)
        {

            this.IUser = IUser;
        }
        
        [Route("UserSync")]
        [HttpPost]
        public ApiResultModel UserSync()
        {
            return IUser.UserSync();
        }

        [Route("UserDelete")]
        [HttpPost]
        public ApiResultModel UserDelete(RequestModel user)
        {
            return IUser.UserDelete(user);
        }
       
    }

Action方法利用Repository属性返回的对象来实现逻辑模块，这个IUserRepository接口类型的属性在构造函数中初始化。我们利用IUserRepository接口来抽象对逻辑功能的实现

，如下面的代码片断所示，我们在此接口中仅定义了两个方法UserSync获取用户信息，UserDelete删除用户。

  public interface IUserRepository
    {
        /// <summary>
        /// UserSync
        /// </summary>
        /// <returns></returns>
         ApiResultModel UserSync();

        /// <summary>
        /// UserDelete
        /// </summary>
        /// <returns></returns>
        ApiResultModel UserDelete(RequestModel user);
    }

创建UserRepository

 public class UserRepository: IUserRepository
    {
  public ApiResultModel UserSync()
        {
//逻辑代码
}

  public ApiResultModel UserDelete(RequestModel user)
{
//逻辑代码
}
}

最后在项目的Global.aspx的自定义的UnityHttpControllerActivator进行了注册。如下所示，我们在Application_Start方法中创建了一个UnityContainer对象，并通过调用泛型方

法RegisterType<TFrom,TTo>注册了IUserRepository接口和UserRepository类型之间的匹配关系。我们最后根据这个UnityContainer创建一个UnityHttpControllerActivator对象，并将其注册到当前ServicesContainer上。

  protected void Application_Start()
        {

            GlobalConfiguration.Configure(WebApiConfig.Register);

            // 使api返回为json 
            GlobalConfiguration.Configuration.Formatters.XmlFormatter.SupportedMediaTypes.Clear();

            //ioc 配置 
            IUnityContainer unityContainer = new UnityContainer();
            
            unityContainer.RegisterType<IAccountRepository, AccountRepository>();
            unityContainer.RegisterType<IApprovalRepository, ApprovalRepository>();
            unityContainer.RegisterType<IMessageRepository, MessageRepository>();
            unityContainer.RegisterType<IAttendanceRepository, AttendanceRepository>();
            unityContainer.RegisterType<ISalaryRepository, SalaryRepository>();
            unityContainer.RegisterType<IDepartmentRepository, DepartmentRepository>();
            unityContainer.RegisterType<ITagRepository, TagRepository>();
            unityContainer.RegisterType<IUserRepository, UserRepository>();


            GlobalConfiguration.Configuration.Services.Replace(typeof(IHttpControllerActivator), new Common.UnityHttpControllerActivator(unityContainer));
        }

一、引用Autofac

首先　还是引入Autofac 包

Global.aspx

   protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();

            WebApiConfig.Register(GlobalConfiguration.Configuration);
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);



            //ioc 
            var builder = new ContainerBuilder();
            SetupResolveRules(builder);
            builder.RegisterControllers(typeof(MvcApplication).Assembly).PropertiesAutowired();
            builder.RegisterAssemblyModules(Assembly.GetExecutingAssembly());

            var container = builder.Build();
            DependencyResolver.SetResolver(new AutofacDependencyResolver(container));
        }

创建方法SetupResolveRules 用于获取当前的依赖注入，

  private void SetupResolveRules(ContainerBuilder builder)
        {
            var Inter = new List<Type>();
            Assembly assembly = Assembly.Load("Car.Core.IRepository");
            foreach (Type aaa in assembly.GetTypes())
            {
                if (aaa.Name.StartsWith("I") && aaa.Name.EndsWith("Repository"))
                {
                    Inter.Add(aaa);
                }
            }

            var entity = new List<Type>();
            Assembly entassembly = Assembly.Load("Car.Core.Repository");
            foreach (Type aaa in entassembly.GetTypes())
            {
                if (aaa.Name.EndsWith("Repository"))
                {
                    entity.Add(aaa);
                }
            }

            foreach (var item in entity)
            {
                Inter.ForEach(a =>
                {
                    if (a.Name.Contains(item.Name))
                    {
                        builder.RegisterType(item).As(a);
                    }
                });
            }


       

        }

IoC在Web API中的应用

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