protected override void OnActionExecuting(ActionExecutingContext filterContext)
{
base.OnActionExecuting(filterContext);
CurrentLanguage = Request?.QueryString[LanguageParam] ?? Languages.First().Key;
CurrentIndex = Request?.QueryString[IndexParam] ?? Indices.FirstOrDefault(i => i.Index.EndsWith($"-{CurrentLanguage}"))?.Index;
CurrentIndexDisplayName = Indices.FirstOrDefault(i => i.Index == CurrentIndex)?.DisplayName;
}