ArrayList Sorting

using System;
using System.Collections;

public class Person : IComparable
{
#region Private Members

private string _firstname;
private string _lastname;
private int _age;

#endregion

#region Properties

public string Firstname
{
get { return _firstname; }
set { _firstname = value; }
}

public string Lastname
{
get { return _lastname; }
set { _lastname = value; }
}

public int Age
{
get { return _age; }
set { _age = value; }
}

#endregion

#region Contructors

public Person(string firstname, string lastname, int age)
{
_firstname = firstname;
_lastname = lastname;
_age = age;
}

#endregion

#region ToString()

public override string ToString()
{
return String.Format("{0} {1}, Age = {2}", _firstname,
_lastname, _age.ToString());
}

#endregion

#region IComparable Members

public int CompareTo(object obj)
{
if (obj is Person)
{
Person p2 = (Person)obj;

return _firstname.CompareTo(p2._firstname);
}
else
throw new ArgumentException("Object is not a Person.");
}

#endregion

public int CompareTo(Person p2, PersonComparer.ComparisonType comparisonMethod)
{
switch (comparisonMethod)
{
case PersonComparer.ComparisonType.Lastname:
return _lastname.CompareTo(p2._lastname);
case PersonComparer.ComparisonType.Age:
return _age.CompareTo(p2._age);
case PersonComparer.ComparisonType.Firstname:
default:
return _firstname.CompareTo(p2._firstname);
}
}

#region PersonComparer

public class PersonComparer : IComparer
{
public enum ComparisonType
{ Firstname = 1, Lastname = 2, Age = 3 }

private ComparisonType _comparisonType;

public ComparisonType ComparisonMethod
{
get { return _comparisonType; }
set { _comparisonType = value; }
}

#region IComparer Members

public int Compare(object x, object y)
{
Person p1;
Person p2;

if (x is Person)
p1 = x as Person;
else
throw new ArgumentException("Object is not of type Person.");

if (y is Person)
p2 = y as Person;
else
throw new ArgumentException("Object is not of type Person.");

return p1.CompareTo(p2, _comparisonType);
}

#endregion
}

#endregion
}


public class TestClass
{
public static void Main()
{
// Create ArrayList
ArrayList people = new ArrayList();
people.Add(new Person("John", "Doe", 76));
people.Add(new Person("Abby", "Normal", 25));
people.Add(new Person("Jane", "Doe", 84));

// Create Person Comparer Class
Person.PersonComparer comparer = new Person.PersonComparer();

// Sort By Lastname
comparer.ComparisonMethod = Person.PersonComparer.ComparisonType.Lastname;
people.Sort(comparer);
Console.WriteLine("Last Name");
TestClass.DisplayPeople(people);

// Sort By Age
comparer.ComparisonMethod = Person.PersonComparer.ComparisonType.Age;
people.Sort(comparer);
Console.WriteLine("Age");
TestClass.DisplayPeople(people);

// Sort By Firstname
comparer.ComparisonMethod = Person.PersonComparer.ComparisonType.Firstname;
people.Sort(comparer);
Console.WriteLine("First Name");
TestClass.DisplayPeople(people);
}

public static void DisplayPeople(ArrayList people)
{
foreach (Person p in people)
Console.WriteLine(p);

Console.ReadLine();
}
}