public ObservableCollection <XacNhanDangKyUser> loadPage(int pageNumber, int numItemInPage)
        {
            var resulf = new ObservableCollection <XacNhanDangKyUser>();

            PagingInfo.ItemInPerPage = numItemInPage;

            if (PagingInfo.TotalPage > 0)
            {
                if (pageNumber > PagingInfo.TotalPage)
                {
                    pageNumber = 1;
                }
                if (pageNumber < 1)
                {
                    pageNumber = PagingInfo.TotalPage;
                }

                PagingInfo.CurrentPage = pageNumber;

                var list = ListDangKyUser.Skip((pageNumber - 1) * PagingInfo.ItemInPerPage).Take(PagingInfo.ItemInPerPage);

                foreach (var item in list)
                {
                    resulf.Add(item);
                }
            }
            else
            {
                PagingInfo.CurrentPage = 0;
            }
            return(resulf);
        }