MEF实现IOC(依赖倒置)

场景: 实现依赖倒置,使用Managed Extensibility Framework（MEF）是扩展性管理框架

准备: 定义好的接口,接口的实现类,引入命名空间,System.ComponentModel.Composition

[在控制台中的实现]

---------------------------------------------------------
namespace ConsoleApplicationDemo.IContract
{
    public interface IExpor
    {
        string GetTxt(string name,string password);
    }
}

---------------------------------------------------------------

using ConsoleApplicationDemo.IContract;
using System.ComponentModel.Composition;
namespace ConsoleApplicationDemo.Impl
{
    [Export("ex1",typeof(IExpor))]
    public class Demo1 : IExpor
    {
        public string GetTxt(string name,string password)
        {
            return string.Format("{0}---{1}",name,password);
        }
    }
}
   ---------------------------------------------------------------

using ConsoleApplicationDemo.IContract;
using System.ComponentModel.Composition;
namespace ConsoleApplicationDemo.Impl2
{
    [Export("ex2",typeof(IExpor))]
    public class Demo1:IExpor
    {
        public string GetTxt(string name,string password)
        {
            return string.Format("****{0}^^^^^^^{1}",password);
        }
    }
}

---------------------------------------------------------------

使用到接口的类:

using System.ComponentModel.Composition;
using ConsoleApplicationDemo.IContract;
namespace ConsoleApplication.Demo
{
    [Export]
    class DemoExpor
    {
        [Import("ex1")]
        public IExpor Expor { get; set; }

        [Import("ex2")]
        public IExpor Expor2 { get; set; }
    }
}

---------------------------------------------------------------

调用:

        static void Main(string[] args)
        {
             

            AggregateCatalog catalog = new AggregateCatalog();
            catalog.Catalogs.Add(new DirectoryCatalog(Directory.GetCurrentDirectory()));
            catalog.Catalogs.Add(new AssemblyCatalog(Assembly.GetExecutingAssembly()));
           
            CompositionContainer tainer = new CompositionContainer(catalog);
            DemoExpor dd= tainer.GetExportedValue<DemoExpor>();

            Console.WriteLine(dd.Expor.GetTxt("N@ME","P@$$W0RD"));
            Console.WriteLine(dd.Expor2.GetTxt("N@ME","P@$$W0RD"));

            Console.Read();

            
        
        }

---------------------------------------------------------------

结果:

----------------------------------------------------------------------------------

MVC4 中MEF实现依赖倒置:

准备:接口,实现类,System.ComponentModel.Composition

---------------------------------------------------------------
namespace MEFIOCDemo
{
    public interface IAccountSiteContract
    {
        string Test(string name,string password);
    }
}

using System.ComponentModel.Composition;
using System.ComponentModel.Composition.Primitives;

    ---------------------------------------------------------------
namespace MEFIOCDemo.Impl
{
   
 [Export(typeof(IAccountSiteContract))]
    public class AccountContract:IAccountSiteContract
    {

        public string Test(string name,string password)
        {
            return string.Format("Name:{0}Password:{1}",password);
        }
    }
}

---------------------------------------------------------------

//创建一个实现 IDependencyResolver 接口的MEF实现类
//Web应用程序的无状态性，即每次访问都是独立进行的，所以IOC组件产生的对象实例也必须唯一
//否则不同用户的操作就可能串线，产生相互干扰。
//使用HttpContext.Current.Items集合来保存 组合容器CompositionContainer的实例，以使每个用户的数据保持独立且同一用户的同一个Http请求中使用同一对象实例。
//另外考虑到可能会有某种情况下需要手动获取组合容器中的实例，把组合容器缓存到了当前上下文中的Application中。
//(参考 http://www.cnblogs.com/guomingfeng/archive/2013/05/21/mvc-ioc-mef.html MVC实用架构设计（二）——使用MEF实用IOC（依赖倒置） )
using System;
using System.Collections.Generic;
using System.ComponentModel.Composition;
using System.ComponentModel.Composition.Hosting;
using System.ComponentModel.Composition.Primitives;
using System.Web.Mvc;
using System.Web;

namespace MEFIOCDemo.IOC
{
    public class IOCDemo:IDependencyResolver
    {
        private ComposablePartCatalog _catalog;

        private const string iocdemokey = "iocdemoKey";

        public IOCDemo(ComposablePartCatalog log)
        {
            _catalog = log;
        }

        public CompositionContainer Container
        {
            get
            {
                if (!HttpContext.Current.Items.Contains(iocdemokey))
                {
                    HttpContext.Current.Items.Add(iocdemokey,new CompositionContainer(_catalog));
                }
                CompositionContainer triner = (CompositionContainer)HttpContext.Current.Items[iocdemokey];
                HttpContext.Current.Application["Container"] = triner;
                return triner;

            }
        }



        public object GetService(Type serviceType)
        {
            string contractName = AttributedModelServices.GetContractName(serviceType);
            return Container.GetExportedValueOrDefault<object>(contractName);
            
        }

        public IEnumerable<object> GetServices(Type serviceType)
        {
            return Container.GetExportedValues<object>(serviceType.FullName);
        }
    }
}

---------------------------------------------------------------

在路由配置中初始化

using MEFIOCDemo.IOC;
using System.ComponentModel.Composition.Hosting;
namespace DemoMVC4
{
    // 注意: 有关启用 IIS6 或 IIS7 经典模式的说明，
    // 请访问 http://go.microsoft.com/?LinkId=9394801

    public class MvcApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();

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


          DirectoryCatalog catalog = new DirectoryCatalog (AppDomain.CurrentDomain.SetupInformation.PrivateBinPath);
           IOCDemo demod = new IOCDemo(catalog);
           DependencyResolver.SetResolver(demod);

        }
         
       
    
    }
}

---------------------------------------------------------------

 使用:

using System.ComponentModel.Composition;
namespace DemoMVC4.Controllers
{
    [Export]
    public class HomeController : Controller
    {
        [Import]
        private MEFIOCDemo.IAccountSiteContract accountContract;
        public ActionResult Index()
        {
            ViewBag.Title = accountContract.Test("ABC","p@ssw0rd");
            return View();
        }

    }
}

页面上:

@{
    ViewBag.Title = ViewBag.Title;
}

<h2>@ViewBag.Title</h2>

结果: