c# - 在 Linq 中按 DayOfWeek 分组

Question

我有这个 Linq 查询，它工作正常

var test = (from c in context.ConsumptionSet
            join pi in context.PropertiesInstanceSet on c.PropertiesInstanceID equals pi.PropertiesInstanceID
            join ep in context.EquipmentPropertiesSet on pi.EquipmentPropertiesID equals ep.EquipmentPropertiesID
            where (ep.EquipmentID == equipmentId && pi.ProprietesName == ProprietesName.Energy && c.Date <= DateTime.Today && c.Date >= EntityFunctions.AddDays(DateTime.Today, -7))
            group c by c.Date.Day into grp
            select new
            {
               test = grp.Key,
               value = (from c2 in grp select c2.Value).Max()

            }).ToList();

但我想通过 DayOfWeek 属性对这些结果进行分组，Linq 似乎不允许这样做，因为当我用 c.Date 替换 group c 时出现此错误。 c.Date.DayOfWeek 的 c 组 的 Day :LINQ to Entities 不支持指定的类型成员“DayOfWeek”

这个问题有解决办法吗？

Answer 1

使用SqlFunctions.DatePart :

var test = (from c in context.ConsumptionSet
            join pi in context.PropertiesInstanceSet on c.PropertiesInstanceID equals pi.PropertiesInstanceID
            join ep in context.EquipmentPropertiesSet on pi.EquipmentPropertiesID equals ep.EquipmentPropertiesID
            where (ep.EquipmentID == equipmentId && pi.ProprietesName == ProprietesName.Energy && c.Date <= DateTime.Today && c.Date >= EntityFunctions.AddDays(DateTime.Today, -7))
            group c by SqlFunctions.DatePart("weekday", c.Date) into grp
            select new
            {
               test = grp.Key,
               value = (from c2 in grp select c2.Value).Max()

            }).ToList();