解讀ASP.NET 5 & MVC6系列教程（7）：依賴注入

public interface ITodoRepository
{
 IEnumerableTodoItem> AllItems { get; }
 void Add(TodoItem item);
 TodoItem GetById(int id);
 bool TryDelete(int id);
}

public class TodoItem
{
 public int Id { get; set; }
 public string Name { get; set; }
}

public class TodoRepository : ITodoRepository
{
 readonly ListTodoItem> _items = new ListTodoItem>();

 public IEnumerableTodoItem> AllItems
 {
 get { return _items; }
 }

 public TodoItem GetById(int id)
 {
 return _items.FirstOrDefault(x => x.Id == id);
 }

 public void Add(TodoItem item)
 {
 item.Id = 1 + _items.Max(x => (int?)x.Id) ?? 0;
 _items.Add(item);
 }

 public bool TryDelete(int id)
 {
 var item = GetById(id);

 if (item == null) { return false; }

 _items.Remove(item);

 return true;
 }
}

//注冊(cè)單例模式，整個(gè)應(yīng)用程序周期內(nèi)ITodoRepository接口的示例都是TodoRepository1的一個(gè)單例實(shí)例
services.AddSingletonITodoRepository, TodoRepository1>();
services.AddSingleton(typeof(ITodoRepository), typeof(TodoRepository1)); // 等價(jià)形式

//注冊(cè)特定實(shí)例模型，整個(gè)應(yīng)用程序周期內(nèi)ITodoRepository接口的示例都是固定初始化好的一個(gè)單例實(shí)例

TodoRepository2
services.AddInstanceITodoRepository>(new TodoRepository2());
services.AddInstance(typeof(ITodoRepository), new TodoRepository2()); // 等價(jià)形式

//注冊(cè)作用域型的類型，在特定作用域內(nèi)ITodoRepository的示例是TodoRepository3
services.AddScopedITodoRepository, TodoRepository3>();
services.AddScoped(typeof(ITodoRepository), typeof(TodoRepository3));// 等價(jià)形式

//獲取該ITodoRepository實(shí)例時(shí)，每次都要實(shí)例化一次TodoRepository4類
services.AddTransientITodoRepository, TodoRepository4>();
services.AddTransient(typeof(ITodoRepository), typeof(TodoRepository));// 等價(jià)形式

//如果要注入的類沒有接口，那你可以直接注入自身類型，比如：
services.AddTransientLoggingHelper>();

public class TodoController : Controller
{
 private readonly ITodoRepository _repository;

 /// 依賴注入框架會(huì)自動(dòng)找到ITodoRepository實(shí)現(xiàn)類的示例，賦值給該構(gòu)造函數(shù)
 public TodoController(ITodoRepository repository)
 {
 _repository = repository;
 }

 [HttpGet]
 public IEnumerableTodoItem> GetAll()
 {
 return _repository.AllItems; //這里就可以使用該對(duì)象了
 }
}

public class TodoController : Controller
{
 // 依賴注入框架會(huì)自動(dòng)找到ITodoRepository實(shí)現(xiàn)類的示例，賦值給該屬性
 [FromServices]
 public ITodoRepository Repository { get; set; }

 [HttpGet]
 public IEnumerableTodoItem> GetAll()
 {
 return Repository.AllItems;
 }
}

@using WebApplication1
@inject ITodoRepository repository
div>
 @repository.AllItems.Count()
/div>

var provider1 = this.Request.HttpContext.ApplicationServices; 當(dāng)前應(yīng)用程序里注冊(cè)的Service
var provider2 = Context.RequestServices; // Controller中，當(dāng)前請(qǐng)求作用域內(nèi)注冊(cè)的Service
var provider3 = Resolver; //Controller中

var _repository1 = provider1.GetService(typeof(ITodoRepository));
var _repository2 = provider1.GetServiceLoggingHelper>();//等價(jià)形式
//上述2個(gè)對(duì)象可能為空

var _repository3 = provider1.GetRequiredService(typeof(ITodoRepository));
var _repository4 = provider1.GetRequiredServiceLoggingHelper>();//等價(jià)形式
//上述2個(gè)對(duì)象肯定不為空，因?yàn)槿绻麨榭盏脑?，?huì)自動(dòng)拋異常出來

public class AppSettings
{
 public string SiteTitle { get; set; }
}

services.ConfigureAppSettings>(app =>
{
 app.SiteTitle = "111";
});

var appSettings = app.ApplicationServices.GetRequiredServiceIOptionsAppSettings>>().Options;

@inject IOptionsAppSettings> AppSettings

title>@AppSettings.Options.SiteTitle/title>

services.AddScopedITodoRepository, TodoRepository>();

var serviceProvider = Resolver;

var scopeFactory = serviceProvider.GetServiceIServiceScopeFactory>(); //獲取Scope工廠類
using (var scope = scopeFactory.CreateScope()) // 創(chuàng)建一個(gè)Scope作用域
{
 var containerScopedService = serviceProvider.GetServiceITodoRepository>(); //獲取普通的實(shí)例
 var scopedService1 = scope.ServiceProvider.GetServiceITodoRepository>(); //獲取當(dāng)前Scope的實(shí)例
 Thread.Sleep(200);
 var scopedService2 = scope.ServiceProvider.GetServiceITodoRepository>(); //獲取當(dāng)前Scope的實(shí)例

 Console.WriteLine(containerScopedService == scopedService1); // 輸出：False
 Console.WriteLine(scopedService1 == scopedService2); //輸出：True
}

var serviceProvider = Resolver;

var outerScopeFactory = serviceProvider.GetServiceIServiceScopeFactory>();
using (var outerScope = outerScopeFactory.CreateScope()) //外部Scope作用域
{
 var innerScopeFactory = outerScope.ServiceProvider.GetServiceIServiceScopeFactory>();
 using (var innerScope = innerScopeFactory.CreateScope()) //內(nèi)部Scope作用域
 {
 var outerScopedService = outerScope.ServiceProvider.GetServiceITodoRepository>();
 var innerScopedService = innerScope.ServiceProvider.GetServiceITodoRepository>();

 Console.WriteLine(outerScopedService == innerScopedService); // 輸出：False
 }
}

app.Use(new FuncRequestDelegate, RequestDelegate>(nextApp => new ContainerMiddleware(nextApp, app.ApplicationServices).Invoke));

public class TestService
{
 private ITodoRepository _repository;
 public TestService(ITodoRepository r)
 {
 _repository = r;
 }

 public void Show()
 {
 Console.WriteLine(_repository.AllItems);
 }
}

services.AddScopedITodoRepository, TodoRepository>();
services.AddSingletonTestService>();

var service = serviceProvider.GetRequiredServiceTestService>();

public class TestService2
{
 [FromServices]
 public ITodoRepository Repository { get; set; }
 public void Show()
 {
 Console.WriteLine(Repository.AllItems);
 }
}

public class TestService3
{
 private IHttpContextAccessor _httpContextAccessor;
 public TestService3(IHttpContextAccessor httpContextAccessor)
 {
 _httpContextAccessor = httpContextAccessor;
 }

 public void Show()
 {
 var httpContext = _httpContextAccessor.HttpContext;//獲取上下文對(duì)象實(shí)例
 Console.WriteLine(httpContext.Request.Host.Value);
 }
}

var service = serviceProvider.GetRequiredServiceTestService3>();
service.Show();

app.UseServices(services =>
{
 services.AddMvc();// AddMvc要在這里注冊(cè)
 var builder = new ContainerBuilder();// 構(gòu)造容器構(gòu)建類
 builder.Populate(services);//將現(xiàn)有的Services路由到Autofac的管理集合中
 IContainer container = builder.Build();
 return container.ResolveIServiceProvider>();//返回AutoFac實(shí)現(xiàn)的IServiceProvider
});

// 需要先刪除void類型的ConfigureServices方法
public IServiceProvider ConfigureServices(IServiceCollection services)
{
 var builder = new ContainerBuilder(); // 構(gòu)造容器構(gòu)建類
 builder.Populate(services); //將現(xiàn)有的Services路由到Autofac的管理集合中
 IContainer container = builder.Build();
 return container.ResolveIServiceProvider>(); //返回AutoFac實(shí)現(xiàn)的IServiceProvider
}

public class AutofacModule : Module
{
 protected override void Load(ContainerBuilder builder)
 {
 builder.Register(c => new Logger())
  .AsILogger>()
  .InstancePerLifetimeScope();

 builder.Register(c => new ValuesService(c.ResolveILogger>()))
  .AsIValuesService>()
  .InstancePerLifetimeScope();
 }
}