Linq:计数大于值的情况

Question

我有一个 linq 查询，它接受日期和端口组合的列表。此查询必须从表 CruiseCalendar 中返回数据，在该表中可以找到这些组合，但前提是计数大于 1。我无法计算出 groupby 和 count 语法。 var ShipRendezvous 是我陷入困境的地方。

        var dateAndPort = (from r in context.CruiseCalendar
                        where r.ShipId == shipId
                        && r.CruiseDayDate >= dateRange.First
                        && r.CruiseDayDate <= dateRange.Last
                        select new DateAndPort
                        {
                            Date = r.CruiseDayDate,
                            PortId = r.PortId
                        });

        var shipRendezvous = (from r in context.CruiseCalendar
                              where (dateAndPort.Any(d => d.Date == r.CruiseDayDate
                              && d.PortId == r.PortId))
                              orderby r.CruiseDayDate // (Added since first posting)
                              select r).ToList();

问候，盖伊

Answer 1

如果我理解正确的话，您正在过滤与 dateAndPort 的任何结果匹配的每个集合，然后希望将其单独分组以获得计数。在分组结果中，您只需要那些出现多次的结果集。

var shipRendezvous = (from r in context.CruiseCalendar
                      where (dateAndPort.Any(d => d.Date == r.CruiseDayDate
                      && d.PortId == r.PortId))
                      select r)
                     .GroupBy(x => x.CruiseDayDate) //Groups by every combination
                     .Where(x => x.Count() > 1) //Where Key count is greater 1
                     .ToList();

根据您的评论，您希望再次展平列表。为此，请使用 SelectMany():

var shipRendezvous = (from r in context.CruiseCalendar
                      where (dateAndPort.Any(d => d.Date == r.CruiseDayDate
                      && d.PortId == r.PortId))
                      select r)
                     .GroupBy(x => x.CruiseDayDate) //Groups by every combination
                     .Where(x => x.Count() > 1) //Where Key count is greater 1
                     .SelectMany(x => x)
                     .ToList();