In my previous posts I discussed how to enable global error handling in ASP.NET MVC and how to inject a logging interface into the error handler. In these posts, I simplified things a bit to get my points across.

In production we don't use a custom ErrorHandlingControllerFactory to configure all Controllers with error handling, nor do we instantiate IExceptionFilters manually. What I described was the Poor Man's Dependency Injection (DI) approach, which I find most appropriate when describing DI concepts.

However, we really use Castle Windsor currently, so the wiring looks a bit different although it's still exactly the same thing that's going on. Neither ErrorHandlingActionInvoker nor LoggingExceptionFilter are any different than I have already described, but for completeness I wanted to share a bit of our Windsor code.

This is how we really wire our Controllers:

container.Register(AllTypes
    .FromAssemblyContaining(representativeControllerType)
    .BasedOn<Controller>()
    .ConfigureFor<Controller>(reg => 
        reg.LifeStyle.PerWebRequest.ServiceOverrides(
            new { ActionInvoker = typeof(
                ErrorHandlingControllerActionInvoker)
                .FullName })));

Most of this statement simply instructs Windsor to scan all types in the specified assembly for Controller implementations and register them. The interesting part is the ServiceOverrides method call that uses Windsor's rather excentric syntax for defining that the ActionInvoker property should be wired up with an instance of the component registered as ErrorHandlingControllerActionInvoker.

Since ErrorHandlingControllerActionInvoker itself expects an IExceptionFilter instance we need to configure at least one of these as well. Instead of one, however, we have two:

container.Register(Component.For<IExceptionFilter>()
    .ImplementedBy<LoggingExceptionFilter>());
container.Register(Component.For<IExceptionFilter>()
    .ImplementedBy<HandleErrorAttribute>());

This is Windsor's elegant way of registering Decorators: you simply register the Decorator before the decorated type, and it'll Auto-Wire everything for you.

Finally, we use a ControllerFactory very similar to the WindsorControllerFactory from the MVC Contrib project.

To reiterate: You don't have to use Castle Windsor to enable global error handling or logging in ASP.NET MVC. You can code it by hand as I've demonstrated in my previous posts, or you can use some other DI Container. The purpose of this post was simply to demonstrate one way to take it to the next level.



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Published

Monday, 14 December 2009 06:59:32 UTC

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