Group-by-in-linq

using System;
using System.Linq;
using System.Collections.Generic;

class Person
{ 
    public int PersonId; 
    public string car  ; 
}

class Result
{ 
   public int PersonId;
   public List<string> Cars; 
}

public class Program
{
    public static void Main()
    {
        List<Person> persons = new List<Person>()
        {
            new Person { PersonId = 1, car = "Ferrari" },
            new Person { PersonId = 1, car = "BMW" },
            new Person { PersonId = 2, car = "Audi"}
        };

        //With Query Syntax

        List<Result> results1 = (
            from p in persons
            group p by p.PersonId into g
            select new Result()
                {
                    PersonId = g.Key, 
                    Cars = g.Select(c => c.car).ToList()
                }
            ).ToList();

        foreach (Result item in results1)
        {
            Console.WriteLine(item.PersonId);
            foreach(string car in item.Cars)
            {
                Console.WriteLine(car);
            }
        }

        Console.WriteLine("-----------");

        //Method Syntax

        List<Result> results2 = persons
            .GroupBy(p => p.PersonId, 
                     (k, c) => new Result()
                             {
                                 PersonId = k,
                                 Cars = c.Select(cs => cs.car).ToList()
                             }
                    ).ToList();

        foreach (Result item in results2)
        {
            Console.WriteLine(item.PersonId);
            foreach(string car in item.Cars)
            {
                Console.WriteLine(car);
            }
        }
    }
}

Source: stackoverflow.com

Similar codes

4 votes216 views3 answers
How to create a singleton in unity
C#Unity
2 votes192 views1 answer
C# cancellationtoken example
C#
0 vote205 views1 answer
Web forms switch page
C#
0 vote184 views1 answer
Handle several buttons' click events
C#
0 vote157 views1 answer
Asp.net core miniprofiler
C#
0 vote159 views1 answer
C# load button image from resource
C#
0 vote222 views1 answer
Unity oculus vibrate
C#Unity
1 vote196 views1 answer
For loop string in c#
C#
0 vote198 views1 answer
C# how to check if a array bool is all true
C#
2 votes179 views2 answers
How to split concat string c#
C#