How can an Attribute prevent the execution of an MVC Action?

Question

In MVC an OutputCacheAttribute is capable to prevent the execution of the action it is decorating (if the relative cache exists)

How to implement the same mechanism with a custom attribute?

In other works I would like to be able to decorate an action, and based on a logic internal to the attribute it will decide whether the action should carry on executing or not.

Additions

I've implemented a mechanism by which if a request to an action arrives with a querystring like flushaction=flush_silent, the custom attribute (which is extending the OutputCacheAttribute) invalidates the cache.

What I would also like to do, is not to execute the Action:

[JHOutputCache(CacheProfile = "ContentPageController.Index")]
public ActionResult Index(string url)
{
     //custom code that should not execute when flushing the cache
}

Answer 1

As JHOutputCache extends OutputCacheAttribute, which derives from ActionFilterAttribute, halting execution of the underlying action is quite simple:

public class JHOutputCacheAttribute : OutputCacheAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        if (condition)
            filterContext.Result = new EmptyResult();
        else
            base.OnActionExecuting(filterContext);
    }
}

You can return any valid ActionResult here, including any custom ActionResult you may have derived.