C# 实体框架：排序依据，然后分组依据

我首先使用实体框架代码，下面的POCO表示数据库中的一个表

public class LogEntry
{
    public int Id {get; set;}
    public DateTimeOffset TimeStamp {get;set;}
    public string Message {get; set;}
    public string CorrelationId {get; set;}
}

CorrelationId不是唯一的。表中通常会有多条具有相同CorrelationId的记录，此字段用于跟踪哪些日志条目对应于哪些请求

然后，我有另一个对象，它允许我按CorrelationId对这些日志条目进行分组。此对象不会映射回数据库中的任何表

public class AuditTrail
{
    public string CorrelationId {get; set;}
    public DateTimeOffset FirstEvent {get; set;}
    public List<LogEntry> LogEntries {get; set;}
}

这给了我一个

IQueryable

，我迭代它来构建AuditTrail对象。问题是记录只在组内排序。例如，我将返回昨天的AuditTrail，后面是一周前的AuditTrail，后面是今天的AuditTrail，但在LogEntries列表中，所有这些条目都已排序。我想要的是AuditTrails根据TimeStamp列按降序返回，以便新的AuditTrails显示在UI上我的表的顶部

我还尝试了此查询（根据）：

---

当我希望所有相关Id都按相关Id重新分组时，这只返回每个相关Id的第一个日志条目。

我想您要查找的是这样的内容：

var audits = (from a in context.LogEntries
             group a by a.CorrelationId into grp
             select new AuditTrail
             {
               CorrelationId = grp.Key,
               FirstEvent = grp.OrderBy(g=>g.TimeStamp).First().TimeStamp,
               LogEntries = grp 
             }).OrderByDescending(a=>a.FirstEvent)

var audits = (from a in context.LogEntries
             group a by a.CorrelationId into grp
             let logentries = grp.OrderByDescending( g => g.TimeStamp)
             select   new AuditTrail
                      {
                          CorrelationId = grp.Key,
                          FirstEvent = logentries.First().TimeStamp,
                          LogEntries = logentries.ToList()
                      }).OrderByDescending( at => at.FirstEvent);

---

目前接受，因为数据看起来是正确的。明天将进行更严格的测试，并在必要时进行更新。好的，如果您有任何问题，请告诉我；）

var audits = (from a in context.LogEntries
             group a by a.CorrelationId into grp
             select new AuditTrail
             {
               CorrelationId = grp.Key,
               FirstEvent = grp.OrderBy(g=>g.TimeStamp).First().TimeStamp,
               LogEntries = grp 
             }).OrderByDescending(a=>a.FirstEvent)

var audits = (from a in context.LogEntries
             group a by a.CorrelationId into grp
             let logentries = grp.OrderByDescending( g => g.TimeStamp)
             select   new AuditTrail
                      {
                          CorrelationId = grp.Key,
                          FirstEvent = logentries.First().TimeStamp,
                          LogEntries = logentries.ToList()
                      }).OrderByDescending( at => at.FirstEvent);