using System;

using System.Collections.Concurrent;

using System.Threading;

using System.Threading.Tasks;

using System.Collections.Generic;

using System.Collections;

using System.Linq;

using System.Dynamic;

​

public class Program

{

    public static void Main()

    {

        var people = new List<Person>()

        {

        new Person()

        {

        Age = 20, Name = "A"

        }

​

        , new Person()

        {

        Age = 30, Name = "B"

        }

​

        , new Person()

        {

        Age = 30, Name = "C"

        }

​

        , new Person()

        {

        Age = 40, Name = "D"

        }

        };

        var rnd = new Random();

        var sort = people.GroupBy(p => p.Age);

        int? foo = 2;// null;

        Console.WriteLine(foo < 10);

            List<int>[] bar = new List<int>[5];

    }

}

​

public class Person

{

    public string Name

    {

        get;

        set;

    }

​

    public int Age

    {

        get;

        set;

    }

​

    public override string ToString()

    {

        return Name;

    }

}