public async Task <IActionResult> PerUserStatistics()
        {
            // RichUser
            var richUsers = await(from user in _context.Users
                                  .Include(U => U.Purchases)
                                  .ThenInclude(P => P.Goods)
                                  let TotalPurchasePrice = user.Purchases.Sum(P => P.Goods.Price)
                                                           orderby TotalPurchasePrice descending
                                                           select new
            {
                UserId    = user.Id,
                UserEmail = BoardHelper.GetHidedUserEmail(user.Email),
                TotalPurchasePrice
            }.ToExpando())
                            .Take(5).ToListAsync();

            // LuckyUser
            var luckyUsers = await(from user in _context.Users
                                   .Include(U => U.Purchases)
                                   .ThenInclude(P => P.ResultItemGoods)
                                   .ThenInclude(RIG => RIG.ItemGoods)
                                   .ThenInclude(IG => IG.Item)
                                   let Lucky = user.Purchases.Sum(P => P.ResultItemGoods.ItemGoods.Probability) / user.Purchases.Count
                                               where user.Purchases.Count > 0
                                               orderby Lucky
                                               select new
            {
                UserId    = user.Id,
                UserEmail = BoardHelper.GetHidedUserEmail(user.Email),
                Lucky,
                TotalPurchaseCount = user.Purchases.Count,
                Items = user.Purchases.Select(P => P.ResultItemGoods.ItemGoods).OrderBy(IG => IG.Probability).Take(5).Select(IG => IG.Item).ToList()
            }.ToExpando())
                             .Take(5).ToListAsync();

            return(PartialView("_PerUserStatistics", new PerUserStatisticsViewModel {
                RichUsers = richUsers, LuckyUsers = luckyUsers
            }));
        }