using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        List<MyItem> l = new List<MyItem>();

        l.Add(new MyItem(){person_id = 1, person_name = "Jim", shirt = "green", cost = 10});

        l.Add(new MyItem(){person_id = 1, person_name = "Jim", shirt = "yellow", cost = 20});

        l.Add(new MyItem(){person_id = 1, person_name = "Jim", shirt = "blue", cost = 30});

        l.Add(new MyItem(){person_id = 2, person_name = "John", shirt = "red", cost = 40});

        l.Add(new MyItem(){person_id = 2, person_name = "John", shirt = "orange", cost = 50});

        l.Add(new MyItem(){person_id = 3, person_name = "Joe", shirt = "purple", cost = 60});

        var groupedList = l.GroupBy(x => new { x.person_id, x.person_name });

        foreach(var groupedItem in groupedList)

        {

            Display(groupedItem.Key.person_id);

            Display(groupedItem.Key.person_name);

            foreach(var item in groupedItem)

            {

                Display(item.shirt);

                Display(item.cost);

            }

        }

    }

    public static void Display(object obj)

    {

        Console.WriteLine(obj);

    }

}

​

public class MyItem{

    public int person_id { get; set; }

    public string person_name { get; set; }

    public string shirt { get; set; }

    public int cost { get; set; }

}