如何在创建 Owner lifetimescope 时自动激活 Autofac 组件？

Question

假设我有以下注册：

builder.RegisterType<ContactsManager>().InstancePerOwned<IDialPad>();

当我创建 Owned<IDialpad> 时，没有 class 在 IDialPad 范围内解析取决于 ContactsManager，因此不会创建 ContactsManager。但我仍然希望它在范围创建时创建。

当我这样做时：

builder.RegisterType<ContactsManager>().InstancePerOwned<IDialPad>().AutoActivate();

它不是在范围创建时激活，而是在 Autofac 容器构建时激活，当然它无法激活。

我知道如果我将对 ContactsManager 的虚假依赖添加到作用域中的任何 class，那么 ContactsManager 将自动创建。但这不是我想要的。

Answer 1

我可以看到很多方法来做你想做的事。

如果可以修改IDialpad注册，就可以使用OnActivated事件。

builder.RegisterType<Foo>()
       .As<IFoo>()
       .InstancePerOwned<IBar>();
builder.RegisterType<Bar>()
       .As<IBar>()
       .OnActivated(e => e.Context.Resolve<IFoo>());

如果您无权访问此注册，您可以创建一个模块来执行相同的操作。

class TestModule : Module
{
    protected override void AttachToComponentRegistration(
        IComponentRegistry componentRegistry,
        IComponentRegistration registration)
    {
        if (registration.Services
              .Any(s => s is IServiceWithType 
                        && ((IServiceWithType)s).ServiceType == typeof(IBar)))
        {
            registration.Activated += (sender, e) =>
            {
                e.Context.Resolve<IFoo>();
            };
        }
    }
}

基于前面的解决方案，您可以提供一种新型服务，当另一个服务被激活时，将指示Autofac激活指定的服务。

最终注册将如下所示：

    ContainerBuilder builder = new ContainerBuilder();
    builder.RegisterModule(new AutoActivateModule());
    builder.RegisterType<Foo>()
            .As<IFoo>()
            .As(AutoActivateService.From<IBar>())
            .InstancePerOwned<IBar>();
    builder.RegisterType<Bar>()
            .As<IBar>();

AutoActivateService 和 AutoActivate 的代码如下：

public class AutoActivateModule : Module
{
    protected override void AttachToComponentRegistration(
        IComponentRegistry componentRegistry,
        IComponentRegistration registration)
    {
        foreach (IServiceWithType typedService in registration.Services.OfType<IServiceWithType>())
        {
            registration.Activated += (sender, e) =>
            {
                Service autoActivateService = AutoActivateService.From(typedService.ServiceType);
                foreach (IComponentRegistration r in componentRegistry.RegistrationsFor(autoActivateService))
                {
                    e.Context.ResolveComponent(r, new Parameter[0]);
                }
            };
        }
    }
}

public class AutoActivateService : Service, IEquatable<AutoActivateService>
{

    public static AutoActivateService From<T>()
    {
        return new AutoActivateService(typeof(T));
    }
    public static AutoActivateService From(Type targetType)
    {
        return new AutoActivateService(targetType);
    }


    private AutoActivateService(Type targetType)
    {
        this._targetType = targetType;
    }


    private readonly Type _targetType;


    public override String Description
    {
        get { return this.ToString(); }
    }
    public Type TargetType
    {
        get
        {
            return this._targetType;
        }
    }


    public Boolean Equals(AutoActivateService other)
    {
        return other != null
               && this._targetType == other._targetType;
    }
    public override Boolean Equals(Object obj)
    {
        return this.Equals(obj as AutoActivateService);
    }
    public override Int32 GetHashCode()
    {
        return this._targetType.GetHashCode();
    }
    public override String ToString()
    {
        return String.Format("Autoactivate service for {0}", this._targetType);
    }
}

您还可以使用 BeginLifetimeScope 事件。

激活 Owned<T> 服务后，将创建一个新的 ILifetimeScope，其标签将是关联的服务。

container.ChildLifetimeScopeBeginning += ChildLifetimeScopeBeginning;

// ...

private static void ChildLifetimeScopeBeginning(
    Object sender, LifetimeScopeBeginningEventArgs e)
{
    e.LifetimeScope.ChildLifetimeScopeBeginning += ChildLifetimeScopeBeginning;

    IServiceWithType typedService = e.LifetimeScope.Tag as IServiceWithType;
    if (typedService != null && typedService.ServiceType == typeof(IBar))
    {
        e.LifetimeScope.Resolve<IFoo>();
    }
}

如何在创建 Owner lifetimescope 时自动激活 Autofac 组件？

How to auto activate Autofac component on creating of Owner lifetimescope?

c#

inversion-of-control

autofac

ioc-container