How to get controller and action name in OnActionExecuting?

You could try the ActionDescriptor of the ActionExecutingContext as follows:

protected override void OnActionExecuting(ActionExecutingContext filterContext)
{
   string actionName = filterContext.ActionDescriptor.ActionName;
   string controllerName = filterContext.ActionDescriptor.ControllerDescriptor.ControllerName
   .....
   base.OnActionExecuting(filterContext);
}