public IActionResult Index(string sortOrder, string searchString, int pageIndex = 1)
        {
            int pageSize = 8;
            int count;
            var dsdocgia = docGiaService.GetDSDocGia(sortOrder, searchString, pageIndex, pageSize, out count);
            var docGia   = new DocGiaDTO();
            var docgiaVM = new DocGiaIndexVm()
            {
                DocGias      = new PaginatedList <DocGiaDTO>(dsdocgia, count, pageIndex, pageSize),
                SearchString = searchString,
                SortOrder    = sortOrder,
                docgia       = docGia
            };

            return(View(docgiaVM));
        }