CODEWITHSUNDEEP
c#asp.net-mvc-4lambda
N8K8
N8K8

Reputation: 287

Using group by and count lambda expression

I need to obtain the following output in a List , I am using MVC4 and C#. Basically the query I need to execute is :

SELECT ESTADO, COUNT(*)
FROM VISITAS
WHERE CICLOID=ID
GROUP BY ESTADO;

In order to achieve this I wrote the following procedure in my Repository:

  public List<object> PorcentajeVisitasCiclo(Guid id)
  {
      return new List<object> {_context.Visitas
          .Where(a => a.CicloId == id)
          .GroupBy(a => a.Estado)
          .Select(n => new { Text = n.Key.Descripcion , Value = n.Count() })};
  }

Could you point me where I am going wrong? It doesnt give any compilation error, however it doesnt return anything

Thankd in advance

Upvotes: 4

Views: 11764

Answers (4)

pata
pata

Reputation: 989

This could be an option. I had same problem and returning a list of object wasnt a solution (some LINQ error i cant remember). I went for easier solution.

public List<DummyModel> Method(int id)
    {
        return _context.Visitas.Where(a => a.CicloId == id).GroupBy(a => a.Estado).
            Select(n => new DummyModel { Name = n.Key.Descripcion, Value = n.Count() }).ToList();
    }

Upvotes: 4

Neel
Neel

Reputation: 11731

return (_context.Visitas.Where(a => a.CicloId == id)
    .GroupBy(a => a.Estado)
    .Select(n => new { Text = n.Key , Value = n.Count() })).Cast<object>().ToList();

Upvotes: 1

Aleksei Chepovoi
Aleksei Chepovoi

Reputation: 3955

You can change Your return type from List<object> to IEnumerable.

BTW, List<object> is equal to List.

You can call ToList() extension method on Your query and return List of objects. But this will force the query to execute immediately and You will not get use of yield return in the future. This is bad in case Your query returns a large amount of data. All data will be loaded into memory when You call ToList().

Upvotes: 1

Heinzi
Heinzi

Reputation: 172270

You create a new List<object> containing one element, which is your LINQ query. That's probably not what you want.

This executes your LINQ query and then converts the result to a list:

return _context.Visitas.Where(a => a.CicloId == id)
    .GroupBy(a => a.Estado)
    .Select(n => new { Text = n.Key.Descripcion , Value = n.Count() }).ToList();

This, however, yields the problem that a List<yourAnonymousType> is not a subtype of List<object>. Hence, you need to cast your anonymous type to object first:

return _context.Visitas.Where(a => a.CicloId == id)
    .GroupBy(a => a.Estado)
    .Select(n => new { Text = n.Key.Descripcion , Value = n.Count() })
    .Cast<object>().ToList();

Of course, a better solution would be to drop the anonymous type and use an explicit class YourDataType with Text and Value fields/properties. Then you can simply return a List<YourDataType>.

Upvotes: 4

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