title: Return View from ActionFilter
body: <p>I have an ActionFilter that checks if a parameter in the URL is valid.
  If it is not valid I have to render a View. I dont want to redirect, because I still need the ActionExecutingContext.
  Can that be done?</p>
  
  <pre><code>    public override void  OnActionExecuting(ActionExecutingContext filterContext)
      {
          Guid processIdentifier = (Guid)filterContext.RouteData.Values["processIdentifier"];
          //if processIdentifier  not found render a view with message and some other objects in ViewData
          filterContext.Controller.ViewData.ModelState.AddModelError("WrongProcessIdentifier", "The process-id you supplied is not valid");
          base.OnActionExecuting(filterContext);
      }
  </code></pre>