c# - Entity Framework 和函数导入的错误消息

Question

我有一个返回 float 的数据库存储过程。 Stored proc 计算输入并根据输入吐出一个“评级”。我能够更新模型并执行函数导入，但是当我尝试在 Linq 中使用新函数时，出现以下错误。

Function metadata used in DbFunctionExpression must allow composition. Non-composable functions or functions that include command text are not allowed in expressions.

我不知道那是什么意思，Google 搜索没有返回任何结果。

相关代码如下:

public static class EntityFunctions
{
    [EdmFunction("RateMyNeighborhoodModel.Store","RMNIndex")]
    public static decimal? RMNIndex
       (
       float Unemployment,
       float AverageCommuteTime,
       float FamiliesBelowPoverty,
       float TotalCrime,
       float PersonalCrime,
       float Murder,
       float Rape,
       float Robbery,
       float Assault,
       float PropertyCrime,
       float Burgulary,
       float Larceny,
       float VehicleTheft,
       float SexOffenderCount
       )
    {
        throw new NotSupportedException();
    }

}


 var neighborhoodViews = (from 
                                     nv in db.NeighborhoodViews 
                                 join
                                     n in db.Neighborhoods.Include("ZipCodeStatistic") on nv.NeighborhoodID equals n.NeighborhoodID
                                 where
                                     EntityFunctions.RMNIndex((float)n.UnemploymentRate, (float)nv.AverageCommuteTime, (float)nv.familiesBelowPoverty, (float)nv.TotalCrime, (float)nv.PersonalCrime, (float)nv.Murder, (float)nv.Rape, (float)nv.Robbery, (float)nv.Assault, (float)nv.PropertyCrime, (float)nv.Burgulary, (float)nv.Larceny, (float)nv.VehicleTheft, (float)n.ZipCodeStatistic.SexOffenders) > 4 
                                 orderby 
                                    Guid.NewGuid() 
                                 select new 
                                 {
                                     City = n.City,
                                     GeographyData = nv.Geography,
                                     ID = n.NeighborhoodID,
                                     Latitude = Single.Parse(nv.Center.Replace("POINT (", "").Replace(")", "").Split(' ')[1]),
                                     Longitude = Single.Parse(nv.Center.Replace("POINT (", "").Replace(")", "").Split(' ')[0]),
                                     Name = n.Name,
                                     State = n.State,
                                     UpdateDate = n.UpdateDate,
                                     RMNIndex = EntityFunctions.RMNIndex((float)n.UnemploymentRate, (float)nv.AverageCommuteTime, (float)nv.familiesBelowPoverty, (float)nv.TotalCrime, (float)nv.PersonalCrime, (float)nv.Murder, (float)nv.Rape, (float)nv.Robbery, (float)nv.Assault, (float)nv.PropertyCrime, (float)nv.Burgulary, (float)nv.Larceny, (float)nv.VehicleTheft, (float)n.ZipCodeStatistic.SexOffenders),
                                     Zipcode = n.ZipCodeStatistic.ZipCode,
                                     TotalCrime = (double)n.ZipCodeStatistic.TotalCrime,
                                     PersonalCrime = (double)n.ZipCodeStatistic.PersonalCrime,
                                     Murder = (double)n.ZipCodeStatistic.Murder,
                                     Rape = (double)n.ZipCodeStatistic.Rape,
                                     Robbery = (double)n.ZipCodeStatistic.Robbery,
                                     Assault = (double)n.ZipCodeStatistic.Assault,
                                     PropertyCrime = (double)n.ZipCodeStatistic.PropertyCrime,
                                     Burgulary = (double)n.ZipCodeStatistic.Burgulary,
                                     Larceny = (double)n.ZipCodeStatistic.Larceny,
                                     VehicleTheft = (double)n.ZipCodeStatistic.VehicleTheft,
                                     AverageCommuteTime = (double)n.ZipCodeStatistic.AverageCommuteTime,
                                     UnemploymentRate = (double)n.ZipCodeStatistic.UnemploymentRate,
                                     FamiliesBelowPoverty = (double)nv.familiesBelowPoverty,
                                     SexOffenderCount = (int)n.ZipCodeStatistic.SexOffenders

                                 }).Take(5);

Answer 1

问题是我使用的是存储过程和函数导入。当我将存储过程转换为标量函数时，我能够按照预期的方式使用它。