IOC运用到MVC中

IOC可以摒弃掉类中类的紧耦合，让设计和重用更简单，将IOC加入到MVC中的实现非常简单，那么有哪几种方法？它们的实现又是什么原理呢？

IOC在MVC中的注入，主要是在获取Controller对象中实现，也就是在获取Controller对象的方法中增加注入的相关实现就可以了，这些入口均是在DefaultControllerFactory类中,目前获取Controller的有如下方法：

（1）重写DefaultControllerFactory中的GetControllerInstance方法

源码：

  protected internal virtual IController GetControllerInstance(RequestContext requestContext, Type controllerType)
        {
            if (controllerType == null)
            {
                throw new HttpException(404,
                                        String.Format(
                                            CultureInfo.CurrentCulture,
                                            MvcResources.DefaultControllerFactory_NoControllerFound,
                                            requestContext.HttpContext.Request.Path));
            }
            if (!typeof(IController).IsAssignableFrom(controllerType))
            {
                throw new ArgumentException(
                    String.Format(
                        CultureInfo.CurrentCulture,
                        MvcResources.DefaultControllerFactory_TypeDoesNotSubclassControllerBase,
                        controllerType),
                    "controllerType");
            }
            return ControllerActivator.Create(requestContext, controllerType);
        }

重写后：

public class DefaultFactoryIOC:DefaultControllerFactory
    {
        private IKernel kernel;
        public DefaultFactoryIOC()
        {
            kernel = new StandardKernel();
            kernel.Bind<IRespo>().To<Respo>();
        }
        protected override IController GetControllerInstance(System.Web.Routing.RequestContext requestContext, Type controllerType)
        {
            return (IController)kernel.TryGet(controllerType);
        }
    }
Global中定义
    ControllerBuilder.Current.SetControllerFactory(new IOCTest.DefaultFactoryIOC());

（2）对前面的方法再一次观察发现，实例化Controller最后是交给了ControllerActivator.Create(requestContext, controllerType)方法，也就是如果能够实现或者重写这个方法就能实现注入，那么ControllerActivator来自于

  public DefaultControllerFactory(IControllerActivator controllerActivator)
            : this(controllerActivator, null, null)
        {
        }

接下来实现IControllerActivator这个接口，完成第二种IOC方法

public class ControllerActivatorIOC:IControllerActivator
    {
        private IKernel kernel;
        public ControllerActivatorIOC()
        {
            kernel = new StandardKernel();
            kernel.Bind<IRespo>().To<Respo>();
        }
        public IController Create(System.Web.Routing.RequestContext requestContext, Type controllerType)
        {
            return (IController)kernel.TryGet(controllerType);
        }
    }
Global中
  protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();

            /*DefaultFactoryController*/
            //ControllerBuilder.Current.SetControllerFactory(new IOCTest.DefaultFactoryIOC());

            IControllerActivator controlleract = new IOCTest.ControllerActivatorIOC();
            DefaultControllerFactory defaultControllerFactory = new DefaultControllerFactory(controlleract);
            ControllerBuilder.Current.SetControllerFactory(defaultControllerFactory);

        }

（3）接着最后一个方法仍然是从IControllerActivator 中，再DefaultContollerFactory这个Controller激活类中，默认调用实现IControllerActivator的类是DefaultControllerActivator，

它实现了以上这个Create方法

  
private Func<IDependencyResolver> _resolverThunk;
public IController Create(RequestContext requestContext, Type controllerType)
            {
                try
                {
                    return (IController)(_resolverThunk().GetService(controllerType) ?? Activator.CreateInstance(controllerType));
                }
                catch (Exception ex)
                {
                    throw new InvalidOperationException(
                        String.Format(
                            CultureInfo.CurrentCulture,
                            MvcResources.DefaultControllerFactory_ErrorCreatingController,
                            controllerType),
                        ex);
                }
            }

从上可知，Create方法最后会采用那个默认的构造或者第三方实现_resolverThunk的类来实现，而这个_resolverThunk就是从IDependencyResolver接口而来，所以实现IDependencyResolver就可以达到DI的目的

    public class DependencyResolverIOC:IDependencyResolver
    {
        private IKernel kernel;
        public DependencyResolverIOC()
        {
            kernel = new StandardKernel();
            kernel.Bind<IRespo>().To<Respo>();
        }
        public object GetService(Type serviceType)
        {
            var obj = this.kernel.TryGet(serviceType);
            return obj;
        }

        public IEnumerable<object> GetServices(Type serviceType)
        {
            return this.kernel.GetAll(serviceType);
        }
    }

// Note: For instructions on enabling IIS6 or IIS7 classic mode, 
    // visit http://go.microsoft.com/?LinkId=9394801
    public class MvcApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();

            /*DefaultFactoryController*/
            //ControllerBuilder.Current.SetControllerFactory(new IOCTest.DefaultFactoryIOC());

            //IControllerActivator controlleract = new IOCTest.ControllerActivatorIOC();
            //DefaultControllerFactory defaultControllerFactory = new DefaultControllerFactory(controlleract);
            //ControllerBuilder.Current.SetControllerFactory(defaultControllerFactory);

            DependencyResolver.SetResolver(new IOCTest.DependencyResolverIOC());

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