Question

The default route in MVC {controller}/{action}/{id} is for the most part quite helpful as is being able to set a default if the incoming url doesn’t include a parameter but is there also a way to specify a default action for when an action doesn’t exist on a controller?

What I want to achieve is being able to have controllers with several specific actions and then its own catchall which uses the url to grab content from a basic CMS.

For example a products controller would be something like:

public class ProductsController: Controller{
    public ActionResult ProductInfo(int id){...}
    public ActionResult AddProduct(){...}
    public ActionResult ContentFromCms(string url){...} 
}

Where the default route would handle /Products/ProductInfo/54 etc but a request url of /Products/Suppliers/Acme would return ContentFromCms("Suppliers/Acme"); (sending the url as a parameter would be nicer but not needed and a parameterless method where I get it from Request would be fine).

Currently I can think of two possible ways to achieve this, either:

Create a new constraint which reflects over a controller to see if it does have an action of a given name and use this in the {controller}/{action}/{id} route thus allowing me to have a more general catchall like {controller}/{*url}.

Override HandleUnknownAction on the controller.

The first approach seems like it would be quite a roundabout way of checking this while for the second I don’t know the internals of MVC and Routing well enough to know how to proceed.

Update

There’s not been any replies but I thought I’d leave my solution incase anyone finds this in future or for people to suggest improvements/better ways

For the controllers I that wanted to have their own catchall I gave them an interface

interface IHasDefaultController
{
    public string DefaultRouteName { get; }
    System.Web.Mvc.ActionResult DefaultAction();
}

I then derived from the ControllerActionInvoker and overrode FindAction. This calls the base FindAction then, if the base returns null and the controller impliments the interface I call FindAction again with the default actionname.

protected override ActionDescriptor FindAction(ControllerContext controllerContext, ControllerDescriptor controllerDescriptor, string actionName)
    {
        ActionDescriptor foundAction = base.FindAction(controllerContext, controllerDescriptor, actionName);
        if (foundAction == null && controllerDescriptor.ControllerType.GetInterface("Kingsweb.Controllers.IWikiController") != null)
        {
            foundAction = base.FindAction(controllerContext, controllerDescriptor, "WikiPage");
        }
        return foundAction;
    }

As I also want parameters from the routing I also replace the RouteData at the start of the default Actionresult on the controller

ControllerContext.RouteData = Url.RouteCollection[DefaultRouteName].GetRouteData(HttpContext);

Answer 1

You approach is quite fine. As a side-note:

replace

controllerDescriptor.ControllerType.GetInterface("Kingsweb.Controllers.IWikiController") != null

with

typeof(Kingsweb.Controllers.IWikiController).IsAssignableFrom(controllerDescriptor.ControllerType)

this is more strongly-typed way then passing in the name of the interface via string: what if you change the namespace tomorrow?..