AutoFac使用方法总结:Part II

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。

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public class MyEvent : IDisposable { public MyEvent(string input) { Console.WriteLine(input); } public MyEvent() { Console.WriteLine("Init"); } public void Dispose() { Console.WriteLine("Dispose"); } }

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public void test_event() { var builder = new ContainerBuilder(); builder.RegisterType<MyEvent>(). OnActivating(e => e.ReplaceInstance(new MyEvent("input"))). OnActivated(e => Console.WriteLine("OnActivated")). OnRelease(e => Console.WriteLine("OnRelease")); using (IContainer container = builder.Build()) { using (var myEvent = container.Resolve<MyEvent>()) { } } }

此时的输出为：

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Init input OnActivated Dispose OnRelease

利用事件可以在构造对象之后调用对象的方法：

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[Fact] public void call_method_when_init() { var builder = new ContainerBuilder(); builder.RegisterType<MyClassWithMethod>().OnActivating(e => e.Instance.Add(5)); IContainer container = builder.Build(); Assert.Equal(5, container.Resolve<MyClassWithMethod>().Index); } public class MyClassWithMethod { public int Index { get; set; } public void Add(int value) { Index = Index + value; } }

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：

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public class ClassA { private readonly ClassB b; public ClassA(ClassB b) { this.b = b; } } public class ClassB { public ClassA A { get; set; } } [Fact] public void circular_dependencies_exception() { var builder = new ContainerBuilder(); builder.Register(c => new ClassB(){A = c.Resolve<ClassA>()}); builder.Register(c => new ClassA(c.Resolve<ClassB>())); IContainer container = builder.Build(); Assert.Throws(typeof(DependencyResolutionException), ()=>container.Resolve<ClassA>()); }

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

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[Fact] public void circular_dependencies_ok() { var builder = new ContainerBuilder(); builder.RegisterType<ClassB>(). PropertiesAutowired(PropertyWiringFlags.AllowCircularDependencies).SingleInstance(); builder.Register(c => new ClassA(c.Resolve<ClassB>())); IContainer container = builder.Build(); Assert.NotNull(container.Resolve<ClassA>()); Assert.NotNull(container.Resolve<ClassB>()); Assert.NotNull(container.Resolve<ClassB>().A); }

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