MVC 3 and DependencyResolver - The Ecstasy and the Agony

by coatta 8/19/2011 2:32:00 PM

I started building my first MVC 3 the other day and came across the DependencyResolver mechanism for incorporating 3rd party inversion of control containers. How I rejoiced! I've been using Castle/Windsor for quite some time and have a nice set of capabilities built on top of its interceptor feature. So, I pull in my utility library, grab a Windsor-specific implementation of IDependencyResolver off the net, and start setting up my constructors for injection. I run my sample app, and it all hangs together. My controllers are being instantiated through Windsor and I'm happily making use of my utilities for tracing, logging, timing, etc.

Now its time to make my little sample a little more realistic. I add some model classes, make my views strongly typed, add some forms which submit data back to the application. Its all pretty straightforward, so I am not expecting any problems when I start it up and navigate to the main page. Sadly, it dies. There is an error message about not being able to create an object because a parameterless constructor cannot be found. Naturally, the error message doesn't tell me which class is causing this problem... After a bit, I find that the problem is my new model objects, but that doesn't really make sense because Windsor shouldn't be looking for a parameterless constructor.

I'm puzzling this out when it hits me: The model objects are not being allocated through Windsor, MVC is instantiating them directly. My rejoicing turns to despair. How could they go to all the trouble of setting up an infrastructure to support inversion of control and then not use it uniformly!? OK, I get that model objects are basically data bags and probably shouldn't be referencing services, but an IoC framework is more than just a way to resolve services. As noted above, I've got a bunch of utilities for tracing, timing, debugging, etc. that are all built on top of the core capabilities of Castle/Windsor. And those utilities are useful for model objects. But I can't use them because someone on the MVC team decided that it didn't make sense to use the dependency resolver for model objects.

Now its off to see what other ways MS can inflict emotional damage on me...


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