3.用Autofac增强容器能力：引入面向切面编程（AOP）的能力

一、核心组件包

• Microsoft.Extensions.Configuration. Abstractions

• Microsoft.Extensions.Configuration

Autofac.Extensions.DependencyInjection

Autofac.Extras.DynamicProxy

 

核心扩展点

public interface IServiceProviderFactory<TContainerBuilder>  //注册第三方容器的入口

 

二、使用

1.在Program.cs添加 UseServiceProviderFactory(new AutofacServiceProviderFactory())

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .UseServiceProviderFactory(new AutofacServiceProviderFactory()) //注册第三方容器的入口
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });

2.在Startup.cs添加注册方法Autofac的注册方法， public void ConfigureContainer(ContainerBuilder builder)  

        public virtual void ConfigureContainer(ContainerBuilder builder)
        {
            builder.RegisterType<MyService>().As<IMyService>();
            #region 命名注册
            builder.RegisterType<MyServiceV2>().Named<IMyService>("service2"); //获取对象是通过service2获取MyServiceV2对象
            #endregion

            #region 属性注册
            builder.RegisterType<MyNameService>();
            builder.RegisterType<MyServiceV2>().As<IMyService>().PropertiesAutowired(); //设置可以属性方式获取注入对象
            #endregion

            #region AOP  
            builder.RegisterType<MyInterceptor>();
            builder.RegisterType<MyNameService>();
            builder.RegisterType<MyServiceV2>().As<IMyService>().PropertiesAutowired().InterceptedBy(typeof(MyInterceptor)).EnableInterfaceInterceptors();
            //InterceptedBy(typeof(MyInterceptor)):使用拦截器MyInterceptor并注入
            //EnableInterfaceInterceptors:允许接口拦截器
            //拦截器：接口拦截器，类拦截器。类拦截器需要把方法设置成virtual

            #endregion

            #region 子容器
            builder.RegisterType<MyNameService>().InstancePerMatchingLifetimeScope("myscope");
            #endregion
        }

拦截器MyInterceptor定义

    public class MyInterceptor : IInterceptor
    {
        public void Intercept(IInvocation invocation)
        {
            Console.WriteLine($"Intercept before,Method:{invocation.Method.Name}");
            invocation.Proceed();
            Console.WriteLine($"Intercept after,Method:{invocation.Method.Name}");
        }
    }

3.使用在Autofac注册的服务

        public ILifetimeScope AutofacContainer { get; private set; }
        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            this.AutofacContainer = app.ApplicationServices.GetAutofacRoot();
            var servicenamed = this.AutofacContainer.Resolve<IMyService>();
            servicenamed.ShowCode();
            var service = this.AutofacContainer.ResolveNamed<IMyService>("service2"); //通过命名方式获取注册服务
            service.ShowCode();

            #region 子容器

            using (var myscope = AutofacContainer.BeginLifetimeScope("myscope"))
            {
                //MyNameService在子容器的生命周期中无论创建多少次都是同一个对象
                //因为MyNameService被注册到子容器myscope中了

                var service0 = myscope.Resolve<MyNameService>();
                using (var scope = myscope.BeginLifetimeScope())
                {
                    var service1 = scope.Resolve<MyNameService>();
                    var service2 = scope.Resolve<MyNameService>();
                    Console.WriteLine($"service1=service2:{service1 == service2}");
                    Console.WriteLine($"service1=service0:{service1 == service0}");
                }
            }
            #endregion
        }