How to achieve a dynamic controller and action method in ASP.NET MVC?

Question

In Asp.net MVC the url structure goes like

http://example.com/{controller}/{action}/{id}

For each "controller", say http://example.com/blog, there is a BlogController.

But my {controller} portion of the url is not decided pre-hand, but it is dynamically determined at run time, how do I create a "dynamic controller" that maps anything to the same controller which then based on the value and determines what to do?

Same thing with {action}, if the {action} portion of my url is also dynamic, is there a way to program this scenario?

Answer 1

Absolutely! You'll need to override the DefaultControllerFactory to find a custom controller if one doesn't exist. Then you'll need to write an IActionInvoker to handle dynamic action names.

Your controller factory will look something like:

public class DynamicControllerFactory : DefaultControllerFactory
{
    private readonly IServiceLocator _Locator;

    public DynamicControllerFactory(IServiceLocator locator)
    {
        _Locator = locator;
    }

    protected override Type GetControllerType(string controllerName)
    {
        var controllerType = base.GetControllerType(controllerName);
            // if a controller wasn't found with a matching name, return our dynamic controller
        return controllerType ?? typeof (DynamicController);
    }

    protected override IController GetControllerInstance(Type controllerType)
    {
        var controller = base.GetControllerInstance(controllerType) as Controller;

        var actionInvoker = _Locator.GetInstance<IActionInvoker>();
        if (actionInvoker != null)
        {
            controller.ActionInvoker = actionInvoker;
        }

        return controller;
    }
}

Then your action invoker would be like:

public class DynamicActionInvoker : ControllerActionInvoker
{
    private readonly IServiceLocator _Locator;

    public DynamicActionInvoker(IServiceLocator locator)
    {
        _Locator = locator;
    }

    protected override ActionDescriptor FindAction(ControllerContext controllerContext,
                                                   ControllerDescriptor controllerDescriptor, string actionName)
    {
            // try to match an existing action name first
        var action = base.FindAction(controllerContext, controllerDescriptor, actionName);
        if (action != null)
        {
            return action;
        }

// @ray247 The remainder of this you'd probably write on your own...
        var actionFinders = _Locator.GetAllInstances<IFindAction>();
        if (actionFinders == null)
        {
            return null;
        }

        return actionFinders
            .Select(f => f.FindAction(controllerContext, controllerDescriptor, actionName))
            .Where(d => d != null)
            .FirstOrDefault();
    }
}

You can see a lot more of this code here. It's an old first draft attempt by myself and a coworker at writing a fully dynamic MVC pipeline. You're free to use it as a reference and copy what you want.

Edit

I figured I should include some background about what that code does. We were trying to dynamically build the MVC layer around a domain model. So if your domain contained a Product class, you could navigate to products\alls to see a list of all products. If you wanted to add a product, you'd navigate to product\add. You could go to product\edit\1 to edit a product. We even tried things like allowing you to edit properties on an entity. So product\editprice\1?value=42 would set the price property of product #1 to 42. (My paths might be a little off, I can't recall the exact syntax anymore.) Hope this helps!

Answer 2

After a little more reflection, there may be a bit simpler way for you to handle the dynamic action names than my other answer. You'll still need to override the default controller factory. I think you could define your route like:

routes.MapRoute("Dynamic", "{controller}/{command}/{id}", new { action = "ProcessCommand" });

Then on your default/dynamic controller you'd have

public ActionResult ProcessCommand(string command, int id)
{
   switch(command)
   {
      // whatever.
   }
}

Answer 3

You need to write your own IControllerFactory (or perhaps derive from DefaultControllerFactory) and then register it with ControllerBuilder.