Convert Datetime to string entity framework

Question

I Have the following Method:

public List<REP_MEDIDORDISPLAY> GetAllMedidoresDisplay()
{          
    return ent.TB_MEDIDOR.Select(x => new REP_MEDIDORDISPLAY
    {
            Data_TOI = x.Data_TOI,
            Elemento = x.Elemento,
            Fase = x.Fase,
            KdKe = x.KD_KE,
            N_Equipamento = x.Numero,
            Tensao = x.Tensao,
            Status =  x.TB_REVISAO.Count > 0 ? "Revisão": 
                      x.TB_CHECAGEM_INTERNA.Count > 0 ? "Checagem interna":
                      x.TB_MESACALIBRACAO.Count > 0 ? "Mesa de calibração":
                      x.TB_HIPOT.Count > 0 ? "Hipot":
                      x.TB_INSPECAO.Count > 0? "Inspeção" :
                      x.TB_AGENDAMENTO.FirstOrDefault(y => y.ID_Medidor == x.ID).Data_Agendamento.HasValue ?
                  --> Error here (x.TB_AGENDAMENTO.FirstOrDefault(y => y.ID_Medidor == x.ID).Data_Agendamento.Value.ToString()) :String.Empty 
    }).ToList<REP_MEDIDORDISPLAY>();
}

But it's firing the following error when I try to convert a DateTime to String:

LINQ to Entities does not recognize the method 'System.String ToString()' method, and this method cannot be translated into a store expression.

I hope you can help me guys, I need that value as string, I can't change that to datetime.

possible duplicate of Entity Framework Convert DateTime to string — Jeroen Vannevel
– Jeroen Vannevel, Commented Oct 18, 2013 at 13:15
I don't see how that would help me. my convert is inside a subquery. — Moondustt
– Moondustt, Commented Oct 18, 2013 at 13:18
If you need this then Put another column to the table containing the date as string. Or write a stored procedure to get the same result. — dvjanm
– dvjanm, Commented Oct 18, 2013 at 13:19
There's no way to convert that to string? if I need to add a new column to the Class I'll have to change a lot of things =/ — Moondustt
– Moondustt, Commented Oct 18, 2013 at 13:21
I am not on my computer to test this but why not use Data_Agendamento.Years + Data_Agendamento. Months + .... — Flood Gravemind
– Flood Gravemind, Commented Oct 18, 2013 at 13:32

tomsullivan1989 · Accepted Answer · 2013-10-18 13:21:24Z

4

Entity Framework does not know how to execute ToString() method in SQL. So you should load the data by using ToList() and then translate into SelectListItem as:

return ent.TB_MEDIDOR.ToList().Select(x => new SelectListItem
{ 
    Data_TOI = x.Data_TOI,
    ...
    // can convert DateTime to String here
})
// Then you can select this as a REP_MEDIDORDISPLAY if you want
.Select(y => new REP_MEDIDORDISPLAY
{
   Data_TOI = y.x.Data_TOI,
   ...
});

answered Oct 18, 2013 at 13:21

tomsullivan1989

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1 Comment

Drew Noakes Over a year ago

Calling ToList where you are will create the full entity. It's probably better to call AsEnumerable after selecting the SelectListItem items, then finishing with the final select.

Andre Lombaard · Accepted Answer · 2013-10-18 13:21:47Z

1

Remember that entity framework is converting your linq query to SQL. The error message is quite clear, it doesn't recognize the .ToString() method.

You will have to retrieve the results using entity framework and then perform the needed DateTime to String conversions.

answered Oct 18, 2013 at 13:21

Andre Lombaard

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