I'm trying to get the master page changed for all my aspx pages. For some reason I'm unable to detect when this function is called for a ascx page instead. Any help in correting this would be appreciated.

protected override void OnActionExecuted(ActionExecutedContext filterContext)
{
    var action = filterContext.Result as ViewResult;
    if (action != null && action.MasterName != "" && Request.IsAjaxRequest())
    {
        action.MasterName = "Ajax";
    }
    base.OnActionExecuted(filterContext);
}