问在Entity Framework或LINQ中选择时，如何将日期列分组为较不精确的格式？

EN

var results = from row in db.SomeTable
              group by new 
              { 
                  row.Date.Year, 
                  row.Date.Month, 
                  row.Date.Day, 
                  row.Date.Hour, 
                  row.Date.Minute 
              } into grp
              select new 
              { 
                  YMDHM = grp.Key
                  SomeAverage = grp.Average(x => x.SomeValueToAverage)
              };

var dictionaryOfAverages = results.ToDictionary(
    x => new DateTime(x.YMDHM.Year, 
                      x.YMDHM.Month,  
                      x.YMDHM.Day,  
                      x.YMDHM.Hour,  
                      x.YMDHM.Minute,  
                      0), 
    x => x.SomeAverage);

var results = from row in db.SomeTable
              group by new row.Date.SubString(0, 16) into grp
              select new 
              { 
                  YMDHM = grp.Key
                  SomeAverage = grp.Average(x => x.SomeValueToAverage)
              };