C# lamda表达式 参考一下 分组

aResults = userStateList.GroupBy(n => n.UserId).Select(g =>
                {
                    return new { UserId = g.Key, xxDuration = xxx };
                })
                 .Where(n => n.UserId > 0)
                 .GroupBy(n => new { n.UserId, n.xxDuration })
                 .Select(g => new UserOnlineTime
                 {
                     UserId = g.Key.UserId,
                     UserName = userStateList.Where(c => c.UserId == g.Key.UserId).Select(c => c.UserName).FirstOrDefault(),
                     Duration = (int)g.Key.xxDuration
                 }).ToList();