linq分组依据并选择内部分组依据给出错误EFcore

如何解决linq分组依据并选择内部分组依据给出错误EFcore

我上课

 public class statisticsDaily
    {
        public string Date { get; set; }
        public Nullable<float> Production { get; set; }
        public Nullable<float> m_wind_speed { get; set; }
        public Nullable<float> Availability { get; set; }
        public string Comments { get; set; }
        public string turbineId { get; set; }
        public string Countries { get; set; }
        
    }

我需要在某些字段上应用聚合函数，并从我的课程中选择其余字段

var rslt = await (from d in db.statMonth.Include(f=>f.MasterData).Where(d=>d.m_turbine_id == IPAddress.Parse(id) && d.m_date >= frm)
                      group d by new { d.m_date.Month,d.m_date.Year} into g 
                      select new statisticsDaily
                      {
                          Year = g.Key.Year// We can access Year Now since we grouped by Year as well
                          Date = CultureInfo.CurrentCulture.DateTimeFormat.GetMonthName(g.Key.Month),Production = g.Sum(s => s.m_energy_prod),m_wind_speed = g.Average(s => s.m_wind_speed),Availability = g.Average(s => s.m_availability),Comments=g.Select(s=>s.Comments).ToString(),Countries=g.select(i=>i.Country).ToString()              
                      }
         ).OrderBy(s=>s.Date).ToListAsync();

它给我错误： LINQ表达式'Select （来源：GroupByShaperExpression：键选择器：CAST（DATE_PART（'month'，v.m_date））AS整数）， ElementSelector：EntityShaperExpression：实体类型：v_stats_daily ValueBufferExpression： ProjectionBindingExpression：空投影成员 IsNullable：错误，选择器：（i）=> i.m_comment）'无法翻译。以一种可以翻译的形式重写查询，或者通过插入对AsEnumerable（），AsAsyncEnumerable（），ToList（）或ToListAsync（）的调用来显式切换到客户端评估

解决方法

这是我最能解决您的查询的问题。

var rslt =
(
    await
    (
        from d in db.statMonth.Include(f => f.MasterData)
        where d.m_turbine_id == IPAddress.Parse(id)
        where d.m_date >= frm
        group d by new { d.m_date.Month,d.m_date.Year } into g
        orderby g.Key.Month
        select new
        {
            Year = g.Key.Year,Date = g.Key.Month,Production = g.Sum(s => s.m_energy_prod),m_wind_speed = g.Average(s => s.m_wind_speed),Availability = g.Average(s => s.m_availability),Comments = g.Select(s => s.Comments).ToArray(),Countries = g.Select(i => i.Country).ToArray(),}
    )
    .ToListAsync()
)
.Select(g => new statisticsDaily
{
    Year = g.Year
    Date = CultureInfo.CurrentCulture.DateTimeFormat.GetMonthName(g.Date),Production = g.Production,m_wind_speed = g.m_wind_speed,Availability = g.Availability,Comments = String.Join(",",g.Comments),Countries = String.Join(",g.Countries),})
.ToList();

您可以检查一下现在遇到什么错误吗？