using System.Collections.Generic;
public int Age {get; set;}
public string Name {get; set;}
public static void Main()
List<Person> people = new List<Person>();
people.Add(new Person{Age = 20, Name = "Mouse"});
people.Add(new Person{Age = 30, Name = "Neo"});
people.Add(new Person{Age = 40, Name = "Morpheus"});
people.Add(new Person{Age = 30, Name = "Trinity"});
people.Add(new Person{Age = 40, Name = "Dozer"});
people.Add(new Person{Age = 40, Name = "Smith"});
var query = people.GroupBy(x => x.Age);
foreach(var result in query)
Console.WriteLine(result.Key);
foreach(var person in result)
Console.WriteLine(person.Name);