我正在尝试创建一个具有以下签名的方法:
void Chain(ContainerBuilder builder, IServiceProvider fallbackServiceProvider)
{
// ...
}
这个想法是Chain
可以按如下方式使用:
IServiceProvider fallbackProvider = someExternalProvider;
var builder = new ContainerBuilder();
// Custom registration might happen before and/or after the call to Chain
builder.Register<MyCustomService>().As<IMyCustomService>();
builder.Register<MyExternalServiceReplacement>.As<IExternalService>();
Chain(builder, someExternalProvider);
IContainer container = builder.Build();
// customService should be a MyCustomService
var customService = container.Resolve<IMyCustomService>();
// replacedService should be overridden by MyExternalServiceReplacement
// even though an IExternalService also exists in someExternalProvider
var replacedService = container.Resolve<IExternalService>();
// nonReplacedService should come from someExternalProvider since
// no IExternalService2 was registered with the ContainerBuilder
var nonReplacedService = container.Resolve<IExternalService2>();
理想情况下,我可以向 ContainerBuilder 注册某种类型的缺失依赖项处理程序。
或者,我可能会通过某种方式来注册一个组件,该组件可以拦截对 Resolve*
、TryResolve*
等的每次调用...这也需要拦截构造函数注入(inject)的依赖解析。
遗憾的是,无法查询 IServiceProvider 以获取它提供的每项服务。我只能调用 fallbackServicProvider
的 object IServiceProvider.GetService(Type serviceType)
方法。
最佳答案
您需要一个自定义的IRegistrationSource
实现:当容器需要提供服务时,它会查询已注册的注册源以获取任何可用的实现。
因此在注册源中,您可以要求您的 IServiceProvider
为您提供给定类型的回退实现。
这里有一篇很好的文章介绍了 Autofac 中的整个注册源:Declarative Context Adapters in Autofac 2
基于此,我拼凑了一个原型(prototype) IRegistrationSource
实现(因此它没有经过全面测试,也没有准备好生产,但它可以与您的示例场景一起使用)什么你可以建立在:
public class MyRegistrationSource : IRegistrationSource
{
private readonly IServiceProvider serviceProvider;
public MyRegistrationSource(IServiceProvider serviceProvider)
{
this.serviceProvider = serviceProvider;
}
public IEnumerable<IComponentRegistration> RegistrationsFor(Service service,
Func<Service, IEnumerable<IComponentRegistration>> registrationAccessor)
{
// there are other registration exists in the container
if (registrationAccessor(service).Any())
return Enumerable.Empty<IComponentRegistration>();
var swt = service as IServiceWithType;
if (swt == null)
return Enumerable.Empty<IComponentRegistration>();
// try to get an instance from the IServiceProvider
var instance = serviceProvider.GetService(swt.ServiceType);
if (instance == null)
return Enumerable.Empty<IComponentRegistration>();
// register the instance in the container
return new[]
{
RegistrationBuilder.ForDelegate(swt.ServiceType,
(c, p) => instance)
.CreateRegistration()
};
}
public bool IsAdapterForIndividualComponents { get { return false; } }
}
你可以这样使用它:
var builder = new ContainerBuilder();
// Custom registration might happen before and/or after the call to Chain
builder.RegisterType<MyCustomService>().As<IMyCustomService>();
builder.RegisterType<MyExternalServiceReplacement>().As<IExternalService>();
//Chain(builder, someExternalProvider);
builder.RegisterSource(new MyRegistrationSource(new ServiceProvider()));
IContainer container = builder.Build();
关于c# - 给定一个 ContainerBuilder,我可以注册一个缺失的依赖处理程序吗?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/22335609/