如何使用 Autofac 注册装饰器：“检测到循环组件依赖项”

Question

I have got a Circular dependency to extend the functionality of an object adding a cache abstraction.

 public class CachedDecorator : IParameter
{
    public CachedDecorator (IParameter decorated);
    ...
}


 public class MyImplementationParameter : IParameter
 {
   ...
 } 

Using .Net core Dependency injection container i can do something like this to create those dependencies and it works:

services.AddSingleton<IParameter>(provider => new CachedDecorator 
(provider.GetRequiredService<MyImplementationParameter >()));

How Can I replicate that declaration using Autofac?

I am trying something like this:

   builder.RegisterType<CachedDecorator>()
  .As<IParameter>()
  .WithParameter(
    new ResolvedParameter(
      (pi, ctx) => pi.ParameterType == typeof(MyImplementationParameter ),
      (pi, ctx) => ctx.Resolve<MyImplementationParameter>()));

But i get a "Circular component dependency detected: "

Answer 1

As of Autofac 4.9, you can register your decorator as follows:

builder.RegisterType<MyImplementationParameter>().As<IParameter>();
builder.RegisterDecorator<CachedDecorator, IParameter>();

See the documentation for more information.