Dependency injection .Net Core Notes

　　.Net Core itself provides a simple framework for DI, DI to meet our basic needs. It depends on the following components, taken from the need to pull down Nuget package.

　　　 Microsoft.Extensions.DependencyInjection.Abstractions

　　Of which there are two more important objects, ServiceCollection and ServiceProvider. The former is DI container, each representative of the set of service instances, provides some basic injection method, the following example

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);

 

　　　　　　　// get the next ServiceProvider any one instance of the same　

            services.AddSingleton<IBookDAL, MemoryBookDAL>();

　　　　　　　// Each ServiceProvider made from, both return a new instance of　
            services.AddTransient <IBookDAL2, MemoryBookDAL2> () ;

　　　　　　　// generates the same at the same scope instances, instances of the same i.e. made under the same ServiceProvider　
            services.AddScoped <IBookDAL3, MemoryBookDAL3> ();
            

　　　　　　　// Get Service

　　　　　　　var s= services.BuildServiceProvider().GetService<IBookDAL>();　　

        }

　　The latter is responsible for maintaining Service instances, including creation and destruction. This object also provides extension points integrate third-party components. It can be obtained by a method BuildServiceProvider IServiceCollection extension interface.

　　This is the .Net Core own DI framework of some basic, very simple to use. In the daily development process, we could use some more professional DI components, we are here to try to use Autofac integrated look.

　　First Nuget package, do not pull the wrong.

Autofac.Extensions.DependencyInjection

　　Integrated follows, ConfigureServices method needs to return the IServiceProvider . Special attention under  builder.Populate (services); Explanatory notes

        public IServiceProvider ConfigureServices(IServiceCollection services)
        {
            services.AddMvc(cfg =>
            {
                var filter = ApplicationContainer.Resolve<DefaultExceptionFilterAttribute>();
                //var filter = services.BuildServiceProvider().GetService<DefaultExceptionFilterAttribute>();
                if (filter != null)
                    cfg.Filters.Add(filter);
            }).SetCompatibilityVersion(CompatibilityVersion.Version_2_2);


            var serviceProvider = AutoFacRegister(services);

            return serviceProvider;

        }

　　　　 GET ApplicationContainer the IContainer {public; Private SET;} 

        public IServiceProvider AutoFacRegister (IServiceCollection Services) 
        { 
            var Builder = new new ContainerBuilder (); 

            // Very Import
             // returns normally does not replace the original IServiceProvider IServicePrivder. Custom ServiceScopeFactory also need to ensure that your custom is ServiceProvider RequestServices returned.
            // See detailed https: // www.cnblogs.com/artech/p/3rd-party-di-integration.html
             // here autofac made a special deal with 
            builder.Populate (Services); 

            builder.RegisterType <MemoryBookDAL> ( ) .as <IBookDAL> () .SingleInstance (); 
            builder.RegisterType<TestPermissionCheckService>().As<IPermissionCheckService>().SingleInstance();
            builder.RegisterType<PermissionCheckAuthorizationHandler>().As<IAuthorizationHandler>();
            builder.RegisterType<DefaultExceptionFilterAttribute>();

            builder.RegisterType<GlobalApiLoggingMiddleware>();
            builder.RegisterType<GlobalExceptionMiddleware>();

            ApplicationContainer = builder.Build();

            return new AutofacServiceProvider(ApplicationContainer);
        }