using System;

using System.Collections;

public class Program

{

    public static void Main()

    {

        ArrayList list = new ArrayList();

        list.Add(new Person("Rual", 30));

        list.Add(new Person("Donna", 25));

        list.Add(new Person("Mary", 27));

        list.Add(new Person("Ben", 44));

        Console.WriteLine("Unsorted people:");

        for (int i = 0; i < list.Count; i++)

        {

            Console.WriteLine("list["+i+"]"+ (list[i] as Person).Name + ((list[i] as Person).Age));

        }

        Console.WriteLine();

        Console.WriteLine(

            "People sorted with default comparer (by age):");

        list.Sort();

        for (int i = 0; i < list.Count; i++)

        {

            Console.WriteLine("(list[i] as Person).Name" + ((list[i] as Person).Age));

        }

        Console.WriteLine();

        Console.WriteLine(

            "People sorted with nondefault comparer (by name):");

        list.Sort(PersonComparerName.Default);

        for (int i = 0; i < list.Count; i++)

        {

            Console.WriteLine("{(list[i] as Person).Name}" + ((list[i] as Person).Age));

        }   

    }

}

​

public class Person : IComparable

{

    public string Name;

    public int Age;

    public Person(string name, int age)

    {

        Name = name;

        Age = age;

    }

    public int CompareTo(object obj)

    {

        if (obj is Person)

        {

            Person otherPerson = obj as Person;

            return this.Age - otherPerson.Age;

        }

        else

        {

            throw new ArgumentException(

                "Object to compare to is not a Person object.");

        }

    }

}

​

public class PersonComparerName : IComparer

{

    public static IComparer Default = new PersonComparerName();

    public int Compare(object x, object y)

    {

        if (x is Person && y is Person)

        {

            return Comparer.Default.Compare(

                ((Person)x).Name, ((Person)y).Name);

        }

        else

        {

            throw new ArgumentException(

                "One or both objects to compare are not Person objects.");

        }

    }

}