Vfrdtyky

How can I group by with multiple columns using lambda?

I saw examples of how to do it using linq to entities, but I am looking for lambda form.

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

if your table is like this

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")});

Further to aduchis answer above - if you then need to filter based on those group by keys, you can define a class to wrap the many keys.

return customers.GroupBy(a => new CustomerGroupingKey(a.Country, a.Gender))

                .Where(a => a.Key.Country == "Ireland" && a.Key.Gender == "M")

                .SelectMany(a => a)

                .ToList();

Where CustomerGroupingKey takes the group keys:

    private class CustomerGroupingKey

    {

        public CustomerGroupingKey(string country, string gender)

        {

            Country = country;

            Gender = gender;

        }



        public string Country { get; }



        public string Gender { get; }

    }

     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();



        }

    }