事件

     AutoFac支持三种事件：OnActivating，OnActivated，OnRelease。OnActivating在注册组件使用之前会被调用，此时可以替换实现类或者进行一些其他的初始化工作，OnActivated在实例化之后会被调用，OnRelease在组件释放之后会被调用。

  public class MyEvent : IDisposable  2  {  3       public MyEvent(string input)  4  {  5  Console.WriteLine(input);  6  }  7 
      public MyEvent()  9  { 10           Console.WriteLine("Init"); 11  } 12 
      public void Dispose() 14  { 15           Console.WriteLine("Dispose"); 16  } 17   }

   public void test_event()  2  {  3         var builder = new ContainerBuilder();  4         builder.RegisterType<MyEvent>().  5             OnActivating(e => e.ReplaceInstance(new MyEvent("input"))).  6             OnActivated(e => Console.WriteLine("OnActivated")).  7             OnRelease(e => Console.WriteLine("OnRelease"));  8 

        using (IContainer container = builder.Build()) 11  { 12             using (var myEvent = container.Resolve<MyEvent>()) 13  { 14  } 15  } 16     }

     此时的输出为：

Init 2 input 3 OnActivated 4 Dispose 5 OnRelease

     利用事件可以在构造对象之后调用对象的方法：

 [Fact]  2     public void call_method_when_init()  3  {  4         var builder = new ContainerBuilder();  5         builder.RegisterType<MyClassWithMethod>().OnActivating(e => e.Instance.Add(5));  6         IContainer container = builder.Build();  7         Assert.Equal(5, container.Resolve<MyClassWithMethod>().Index);  8  }  9 
  public class MyClassWithMethod 11  { 12       public int Index { get; set; } 13       public void Add(int value) 14  { 15           Index = Index + value; 16  } 17   }

 

     循环依赖

     循环依赖是个比较头疼的问题，在AutoFac中很多循环依赖的场景不被支持：

  public class ClassA  2  {  3       private readonly ClassB b;  4 
      public ClassA(ClassB b)  6  {  7           this.b = b;  8  }  9  } 10 
  public class ClassB 12  { 13       public ClassA A { get; set; } 14       
 } 16  
 [Fact] 18     public void circular_dependencies_exception() 19  { 20         var builder = new ContainerBuilder(); 21         builder.Register(c => new ClassB(){A = c.Resolve<ClassA>()}); 22         builder.Register(c => new ClassA(c.Resolve<ClassB>())); 23         IContainer container = builder.Build(); 24         Assert.Throws(typeof(DependencyResolutionException), ()=>container.Resolve<ClassA>()); 25     }

     可以部分的解决这种循环依赖的问题，前提是ClassA和ClassB的生命周期不能都是InstancePerDependency

 [Fact]  2     public void circular_dependencies_ok()  3  {  4         var builder = new ContainerBuilder();  5         builder.RegisterType<ClassB>().  6  PropertiesAutowired(PropertyWiringFlags.AllowCircularDependencies).SingleInstance();  7         builder.Register(c => new ClassA(c.Resolve<ClassB>()));  8         IContainer container = builder.Build();  9         Assert.NotNull(container.Resolve<ClassA>()); 10         Assert.NotNull(container.Resolve<ClassB>()); 11         Assert.NotNull(container.Resolve<ClassB>().A); 12     }

 

转载链接：http://niuyi.github.io/blog/2012/04/06/autofac-by-unit-test-2/