How can I load multiple controller factories and pass control on to the next one?

Question

I've created a generic controller factory to load entities from the database by parsing out the url:

entity/products/123456.htm

However, I'd like to be able to load an actual controller if the entity is not found, or to override the default entity behavior if necessary by creating a physical controller, instead of a "virtual" one created by the URL pattern.

Right now, in global.asax.cs I'm doing:

ControllerBuilder.Current.SetControllerFactory(typeof(EntityControllerFactory));

How can I, either in EntityControllerFactory, or here in global.asax.cs, pass control on to another factory, in the event that I'd like MVC's default controller/action scheme to take over?

Answer 1

You could create a composite IControllerFactory implementation:

public class EntityControllerFactory : IControllerFactory {
    private IControllerFactory defaultFactory = new DefaultControllerFactory();

    public IController CreateController(RequestContext requestContext, string controllerName) {
        if(needsCustomLogic) {
            // do your custom logic here and return appropriate result
        } else {
            return defaultFactory.CreateController(requestContext, controllerName);
        }
    }

    // same for the other methods on IControllerFactory
}

This works because by default the value of ControllerBuilder.Current.GetControllerFactory() is an instance of DefaultControllerFactory.

You might also consider making your factory more future-proof (in case a new version of MVC starts returning a different type from GetControllerFactory; unlikely but it could happen) by getting the default instance and passing it into your factory:

// in Global.asax
var defaultFactory = ControllerBuilder.Current.GetControllerFactory();
ControllerBuilder.Current.SetFactory(new EntityControllerFactory(defaultFactory));