CODEWITHSUNDEEP
c#wcfdependency-injectionautofac
Marc
Marc

Reputation: 3959

How to inject WCF Service Implementation into another WCF Service with Autofac

I have multiple WCF Services hosted in IIS and configured with Autofac.

Global.asax

var builder = new ContainerBuilder();

builder.RegisterType<ServiceA>();
builder.RegisterType<ServiceB>();
builder.RegisterType<ServiceC>();

var container = builder.Build();
AutofacHostFactory.Container = container;

web.config

<system.serviceModel>
  ...
  <serviceHostingEnvironment aspNetCompatibilityEnabled="true" multipleSiteBindingsEnabled="true">
    <serviceActivations>
      <add service="ServiceA, MyServicesAssembly" relativeAddress="./ServiceA.svc" factory="Autofac.Integration.Wcf.AutofacServiceHostFactory, Autofac.Integration.Wcf" />
      <add service="ServiceB, MyServicesAssembly" relativeAddress="./ServiceB.svc" factory="Autofac.Integration.Wcf.AutofacServiceHostFactory, Autofac.Integration.Wcf" />
      <add service="ServiceC, MyServicesAssembly" relativeAddress="./ServiceC.svc" factory="Autofac.Integration.Wcf.AutofacServiceHostFactory, Autofac.Integration.Wcf" />
    </serviceActivations>
  </serviceHostingEnvironment>
<system.serviceModel>

Service Implementations

public class ServiceA : IServiceA 
{
    public ServiceA()
    {            
    }
}

public class ServiceB : IServiceB
{
    public ServiceB()
    {            
    }
}

public class ServiceC : IServiceC
{
    public ServiceC(IServiceA serviceA)
    {            
    }
}

As you can see, ServiceC is different from the others and need an implementation of IServiceA. Autofac can't resolve it, because there is no registration for IServiceA.

So I change the registration to this:

builder.RegisterType<ServiceA>().As<IServiceA>();

Autofac can now resolve ServiceC successfully, but the WCF hosting is not working anymore:

An exception of type 'System.ServiceModel.ServiceActivationException' occurred in mscorlib.dll but was not handled in user code

So my question is:

Is there a way that I can have both, a hosted WCF Service instance, and the possibility to pass a Service Implementation to another Service? All configured with AutoFac? I'm also thinking of a workaround, but everything that comes to my mind results in a huge effort. I know that these services needs to be refactored, so that there is no need to pass in another "service". But this is a different story.

Upvotes: 3

Views: 1081

Answers (1)

Nkosi
Nkosi

Reputation: 246998

If you want to expose a component as a set of services as well as using the default service, use the AsSelf method:

//...

builder.RegisterType<ServiceA>()
    .AsSelf() //<--
    .As<IServiceA>();

//...

This will associate the class and interface together so that IServiceA can be injected as needed and it will be resolved to ServiceA. This also allow the WCF to not break as ServiceA is registered.

Reference Autofac Documentation: Registration Concepts

Upvotes: 3

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