的GroupBy DAYOFWEEK Linq中

Question

我有這樣的Linq查詢，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(); 

但我想這組結果由DayOfWeek財產，而且好像LINQ的不允許它，因爲我得到這個錯誤時，我將替換爲group c by c.Date.DayOfWeek： The specified type member 'DayOfWeek' is not supported in LINQ to Entities

是否有解決此問題的方法？

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();