Agrupar por varias columnas usando lambda

Question

¿Cómo puedo agruparme con varias columnas usando lambda?

Vi ejemplos de cómo hacerlo usando linq para entidades, pero estoy buscando la forma lambda.

Answer 1

var query = source.GroupBy(x => new { x.Column1, x.Column2 }); 

Answer 2

si la tabla es así

rowId  col1 col2 col3 col4 
1   a  e  12  2 
2   b  f  42  5 
3   a  e  32  2 
4   b  f  44  5 


var grouped = myTable.AsEnumerable().GroupBy(r=> new {pp1 = r.Field<int>("col1"), pp2 = r.Field<int>("col2")}); 

Answer 3

Además de aduchis respuesta anterior - si este caso es necesario filtrar en función de los grupos de teclas, se puede definir una clase para envolver las muchas claves.

return customers.GroupBy(a => new CustomerGroupingKey(a.Country, a.Gender)) 
       .Where(a => a.Key.Country == "Ireland" && a.Key.Gender == "M") 
       .SelectMany(a => a) 
       .ToList(); 

Dónde CustomerGroupingKey toma las claves de grupo:

private class CustomerGroupingKey 
    { 
     public CustomerGroupingKey(string country, string gender) 
     { 
      Country = country; 
      Gender = gender; 
     } 

     public string Country { get; } 

     public string Gender { get; } 
    } 

Answer 4

 class Element 
     { 
      public string Company;   
      public string TypeOfInvestment; 
      public decimal Worth; 
     } 

    class Program 
    { 
     static void Main(string[] args) 
     { 
     List<Element> elements = new List<Element>() 
      { 
       new Element { Company = "JPMORGAN CHASE",TypeOfInvestment = "Stocks", Worth = 96983 }, 
       new Element { Company = "AMER TOWER CORP",TypeOfInvestment = "Securities", Worth = 17141 }, 
       new Element { Company = "ORACLE CORP",TypeOfInvestment = "Assets", Worth = 59372 }, 
       new Element { Company = "PEPSICO INC",TypeOfInvestment = "Assets", Worth = 26516 }, 
       new Element { Company = "PROCTER & GAMBL",TypeOfInvestment = "Stocks", Worth = 387050 }, 
       new Element { Company = "QUASLCOMM INC",TypeOfInvestment = "Bonds", Worth = 196811 }, 
       new Element { Company = "UTD TECHS CORP",TypeOfInvestment = "Bonds", Worth = 257429 }, 
       new Element { Company = "WELLS FARGO-NEW",TypeOfInvestment = "Bank Account", Worth = 106600 }, 
       new Element { Company = "FEDEX CORP",TypeOfInvestment = "Stocks", Worth = 103955 }, 
       new Element { Company = "CVS CAREMARK CP",TypeOfInvestment = "Securities", Worth = 171048 }, 
      }; 

      //Group by on multiple column in LINQ (Query Method) 
      var query = from e in elements 
         group e by new{e.TypeOfInvestment,e.Company} into eg 
         select new {eg.Key.TypeOfInvestment, eg.Key.Company, Points = eg.Sum(rl => rl.Worth)}; 



      foreach (var item in query) 
      { 
       Console.WriteLine(item.TypeOfInvestment.PadRight(20) + " " + item.Points.ToString()); 
      } 


      //Group by on multiple column in LINQ (Lambda Method) 
      var CompanyDetails =elements.GroupBy(s => new { s.Company, s.TypeOfInvestment}) 
           .Select(g => 
              new 
              { 
               company = g.Key.Company, 
               TypeOfInvestment = g.Key.TypeOfInvestment,    
               Balance = g.Sum(x => Math.Round(Convert.ToDecimal(x.Worth), 2)), 
              } 
            ); 
      foreach (var item in CompanyDetails) 
      { 
       Console.WriteLine(item.TypeOfInvestment.PadRight(20) + " " + item.Balance.ToString()); 
      } 
      Console.ReadLine(); 

     } 
    }