Microsoft Unity base class interception

Question

I have an application that has a base class and derived classes from it with each implementation class having it's own interface. I would like to use Unity's interception for exception handling on derived types of a base class.

I am new to interception so I don't know all the quirks. As far as I know, I have to register interception with each implementation resolve. The point is that all of my implementations have a base class, so I thought that I could skip the redundancy and set the interception on base class only, which would fire on each implementation class.

This is my setting:

public class NotificationViewModel
{
   // some properties
}

public class CompanyViewModel : NotificationViewmodel
{
   // some properties
}

public class BaseService
{
}

public interface ICompanyService
{
   public NotificationViewModel Test();
}

public class CompanyService : BaseService, ICompanyService
{
   public CompanyViewModel Test()
   {
      // call exception
   }
}

public class TestUnityContainer : UnityContainer
{
   public IUnityContainer RegisterComponents()
   {
      this
         .AddNewExtension<Interception>()
         .RegisterType<ICompanyService, CompanyService>(
            new Interceptor<InterfaceInterceptor>(),
            new InterceptionBehavior<TestInterceptionBehavior>());

      return this;
    }
}

public class TestInterceptionBehavior : IInterceptionBehavior
{
   public IEnumerable<Type> GetRequiredInterfaces()
   {
      return new[] { typeof( INotifyPropertyChanged ) };
   }

   public IMethodReturn Invoke( IMethodInvocation input, GetNextInterceptionBehaviorDelegate getNext )
   {
      IMethodReturn result = getNext()( input, getNext );

      if( result.Exception != null && result.Exception is TestException )
      {             
         object obj = Activator.CreateInstance( ( ( System.Reflection.MethodInfo )input.MethodBase ).ReturnType );
         NotificationViewModel not = ( NotificationViewModel )obj;
         // do something with view model
         result.ReturnValue = obj;
         result.Exception = null;
      }

      return result;
   }

   public bool WillExecute
   {
      get { return true; }
   }
}

This works fine, but I would like to have something like this in TestUnityContainer

public class TestUnityContainer : UnityContainer
{
   public IUnityContainer RegisterComponents()
   {
      this
         .AddNewExtension<Interception>()
         .RegisterType<BaseService>(
            new Interceptor<InterfaceInterceptor>(),
            new InterceptionBehavior<TestInterceptionBehavior>() );
         .RegisterType<ICompanyService, CompanyService>();

      return this;
    }
}

I will have many more service classes inheriting from base service and I thought this would save me a lot of time because they all have the same interception behavior.

Is this possible with Unity and how? If some minor corrections to the model are necessary, I am open for them, as long as they are minor.

score 0 · Answer 1 · answered Apr 30 '13 at 21:25

I would suggest you look at Policy Injection in Unity rather than manually applying behaviours on types. With policies you must:-

Create an class that implements ICallHandler (basically a cut down IInterceptionBehavior) - this would be your exception handler behavior.
Create a policy that has "matching rules" - in your case, a policy that uses your CallHandler for any registered types that implement BaseService or similar.
You will still have to register all your services into Unity, but now pass in the Interceptor and InterceptionBehavior. If you have many services, I would suggest looking at something like my Unity Automapper which will simplify both registration and having to mess around with interception behaviors.

Microsoft Unity base class interception

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