C＃如何按时间戳分组记录？ [英] C# how to group records by timestamp?

问题描述

我正在使用C＃NHibernate创建一个仪表板，我想要做的是按时间戳对记录进行分组，所以如果有相同的时间戳，它只会显示一次。我已经尝试过Last（t => t.timestamp）但是收到错误，无法将类型System.DateTime转换为bool，当我尝试.GroupBy（t => t.timestamp）时，我得到< IGrouping< DateTime，Answer> ;不包含eventId，userId和timestamp字段的定义。







开放给建议。谢谢



我的尝试：

I am using C# NHibernate to create a dashboard and what I am trying to do is group the records by timestamp so if there are identical timestamps it will only show once. I have tried Last(t => t.timestamp) but receive the error of cannot convert type System.DateTime to bool and when I tried .GroupBy(t => t.timestamp) I get <IGrouping<DateTime, Answer> does not contain a definition for my fields of eventId, userId, and timestamp.



Open to suggestions. Thanks

What I have tried:

public ActionResult Dashboard()
        {
            using (ISession session = OpenNHibernateSession.OpenSession())
            {

               /*These answers gets my list of data. Here is where I am trying 
                 to use a GroupBy clause so records with identical timestamps
                 will only be shown once.*/
                var answers = session.Query<Answer>().OrderByDescending(t => t.timestamp).ToList();
               
                var dashboardVms = new List<DashboardViewModel>();
                foreach (var answer in answers)
                {
                    var dashboardVm = new DashboardViewModel
                    {
                        EventName = session.Get<Event>(answer.eventId, LockMode.Read).name,
                        EventId = answer.eventId,
                        UserId = answer.userId,
                        TimeStamp = answer.timestamp
                    
                    };
                    dashboardVms.Add(dashboardVm);
                }
                
                return View(dashboardVms);
            }
             
        }

推荐答案

我认为你可以这样做：

I think you can do something like this:

session
    .Query<Answer>()
    .OrderByDescending(t => t.timestamp)
    .GroupBy(x => x.timestamp)
    .Select(x => new
    {
        EventName = session.Get<Event>(x.eventId, LockMode.Read).name,
        EventId = x.eventId,
        UserId = x.userId,
        TimeStamp = x.Key
    }).ToList();

你如果Select调用与您的提供商不兼容，可能希望在GroupBy和select之间链接AsEnumerable调用。

You might want to chain an AsEnumerable call between the GroupBy and the select if the Select call in not compatible with your provider.

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