How to assign value from properties to enum in linq

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This query returns 4 records (2x is IdStandard = 2) - I need 3 records with unique IdStandard and PrimaryCalcMethod and SecondaryCalcMethod methods. If the latter method is not present, the SecondaryCalcMethod property is to return null. How to change the linq query?

System.NotSupportedException: LINQ to Entities does not recognize the method 'AppForSellers.Models.BusinessLogic.SpiralStairs.Models.DiamDivide ParseDiamDivide' method, and this method cannot be translated into a store expression.

What I have tried:

C#

public List<standardent> ListStandardsWithMethodList()
{
    var listModel =
        (
        from dane in _dbContext.Standard
        join kraj in _dbContext.CountryStandard
        on dane.IdCountryStandard equals kraj.IdCountryStandard
        join opcja in _dbContext.MeasureDiameterOption
        on dane.IdStandard equals opcja.IdStandard
        join metoda in _dbContext.MeasureDiameterMethod
        on opcja.IdMeasureDiameterMethod equals metoda.IdMeasureDiameterMethod
        join sposob in _dbContext.WalkingLineRadius
        on opcja.IdWalkingLineRadius equals sposob.IdWalkingLineRadius
        join linia in _dbContext.CalcMethodType
        on sposob.IdCalcMethodType equals linia.IdCalcMethodType
        join wyznaczanie in _dbContext.WalkingLineMeasure
        on sposob.IdWalkingLineMeasure equals wyznaczanie.IdWalkingLineMeasure
        select new StandardEnt()
        {
            IdStandard = dane.IdStandard,
            IdCountryStandard = dane.IdCountryStandard,
            StandardName = dane.StandardName,
            IsActive = dane.IsActive,
            NameCountry = kraj.NameCountryStandard,
            FreeHeadSpace = (double)dane.FreeHeadSpace,
            IsTlcStandard = dane.IsTlcStandard,
            MinLandingSize = (double)dane.MinLandingSize,
            MinStepHeight = (double)dane.MinStepHeight,
            MaxStepHeight = (double)dane.MaxStepHeight,
            MinConvinience = (double)dane.MinConvinience,
            MaxConvinience = (double)dane.MaxConvinience,
            MaxStepDeep = (double)dane.MaxStepDeep,
            MinStepDeep = (double)dane.MinStepDeep,
            MaxStepWidth = (double)dane.MaxStepWidth,
            WidthLimit = (double)dane.WidthLimit,
            StartOverlap = (double)dane.StartOverlap,
            InternalHandrailMaxRadius = (double)dane.InternalHandrailMaxRadius,
            PrimaryCalcMethod = (from metody in _dbContext.MeasureDiameterOption
                                 where dane.IdStandard == metody.IdStandard && metody.MeasureDiameterMethod.CalcMethodName == "PrimaryCalcMethod"
                                 select new MeasureDiameterMethodEnt()
                                 {
                                     IdMeasureDiameterOption = opcja.IdMeasureDiameterOption,
                                     Description = opcja.Description,
                                     IdMeasureDiameterMethod = metoda.IdMeasureDiameterMethod,
                                     IdWalkingLineRadius = sposob.IdWalkingLineRadius,
                                     IdCalcMethodType = linia.IdCalcMethodType,
                                     IdWalkingLineMeasure = wyznaczanie.IdWalkingLineMeasure,
                                     CalcMethod = Enum.Parse<diamdivide>(linia.CalcMethodNameType),
                                     WalkingLineMeasure = Enum.Parse<walkinglinemeasuremethod>(wyznaczanie.WalkingLineMeasureName),
                                     CalcMethodName = metoda.CalcMethodName,
                                     FirstWidth = (double)sposob.FirstWidth,
                                     SecondWidth = (double)sposob.SecondWidth
                                 }).FirstOrDefault(),
            SecondaryCalcMethod = (from metody in _dbContext.MeasureDiameterOption
                                   where dane.IdStandard == metody.IdStandard && metody.MeasureDiameterMethod.CalcMethodName == "SecondaryCalcMethod"
                                   select new MeasureDiameterMethodEnt()
                                   {
                                       IdMeasureDiameterOption = opcja.IdMeasureDiameterOption,
                                       Description = opcja.Description,
                                       IdMeasureDiameterMethod = metoda.IdMeasureDiameterMethod,
                                       IdWalkingLineRadius = sposob.IdWalkingLineRadius,
                                       IdCalcMethodType = linia.IdCalcMethodType,
                                       IdWalkingLineMeasure = wyznaczanie.IdWalkingLineMeasure,
                                       CalcMethod = Enum.Parse<diamdivide>(linia.CalcMethodNameType),
                                       <code></code>                                               WalkingLineMeasure = Enum.Parse<walkinglinemeasuremethod>(wyznaczanie.WalkingLineMeasureName),
                                       CalcMethodName = metoda.CalcMethodName,
                                       FirstWidth = (double)sposob.FirstWidth,
                                       SecondWidth = (double)sposob.SecondWidth
                                   }).FirstOrDefault()
        }
    ).ToList();
    return listModel;
}

Posted 18-Mar-21 6:43am

Szkaradek-Przemyslaw

Updated 6-Apr-21 11:13am

Richard MacCutchan

v2

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[no name] 18-Mar-21 15:43pm

Write "intermediate" queries that string together so it's easier to "debug".

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Jason Sultana · Answer 1 · 2021-04-06T11:13:00

Whenever you get a `LINQ to Entities does not recognize the method abc`, it indicates that you're trying to use some method that can't be converted into SQL. From the looks of it, it could be this:

CalcMethod = Enum.Parse<diamdivide>(linia.CalcMethodNameType),

Instead of calling `Enum.Parse(...)` in your LINQ-to-entities (which of course can't be converted to SQL), try just returning `linia.CalcMethodNameType`. Then, after calling `ToList()` once (which will execute the SQL), parse the enum and return the result.

As a general rule, whenever you need to to complex mapping or parsing, you'll likely have a 2-step process. The first step is to read the data from the database, and call `ToList()` (or equivalent). The second step is to do the mapping / parsing on the result.

Hope that made sense.