Query Linq group by

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Query Linq group by

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#1 by (2 votes)

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I want to build a linq query by applying group by but I have an extended class in which I have to match the feature class with the extended class.

IEnumerable<ModeloExtend> result = Context.Modelos
                                                .Where(x => x.LineaId == damas || x.LineaId == caballeros)
                                                .GroupBy(x => x.LineaId)
                                                .Select(g => new ModeloExtend
                                                {
                                                    ModeloExtendId = g.Key,
                                                    Descripcion = g.ElementAt()
                                                }).ToList();

I can not make the new selection

I want to do this but with GROUP BY eliminating the ORDER BY

List<ModeloExtend> result = Context.Modelos
                .Where(x => x.LineaId == damas || x.LineaId == caballeros)
                .OrderBy(x => x.LineaId)
                .Select(x => new ModeloExtend
                {
                    ModeloExtendId = x.ModeloId,
                    Descripcion = x.Descripcion 
                }).ToList();

c# visual-studio-2015

asked by Pedro Ávila 03.07.2016 в 19:24

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1 answer

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score 2 · Accepted Answer

In the linq that you define you are only defining simple properties of the entity Modelos does not apply the GROUP BY, at most you would use the DISTINCT ()

[Linq] Distinct and GroupBy using IEquatable < >

in this way duplicates of models will not appear

List<ModeloExtend> result = Context.Modelos
                .Where(x => x.LineaId == damas || x.LineaId == caballeros)
                .Select(x => new ModeloExtend
                {
                    ModeloExtendId = x.ModeloId,
                    Descripcion = x.Descripcion 
                }).Distinct().ToList();

Remember to implement the interface IEquatable<> in class ModeloExtend to be able to determine when entities are duplicated