转：http://niuyi.github.io/blog/2012/04/06/autofac-by-unit-test-2/
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>())
{
}
}
}
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此时的输出为：
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Init
input
OnActivated
Dispose
OnRelease
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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;
}
}
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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>());
}
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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);
}
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