using System;

using System.Collections;       

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        List<Person> students = new List<Person>();

        students.Add(new Person("Adam", 18, 180, "1960-01-05"));

        students.Add(new Person("Billy", 19, 190, "1984-12-11"));

        students.Add(new Person("Cristina", 16, 260, "1955-07-04"));

        students.Add(new Person("Debbie", 19, 210, "1984-12-11"));

        students.Sort();

        foreach (Person student in students)

        {

            Console.WriteLine(student.ToString());

        }

    }

}

​

public class Person: IComparable<Person>

{

    public string Name;

    public int Age;

    public int Weight;

    public DateTime BirthDate;

    public Person(string name, int age, int weight, string birthdate)

    {

        Name = name;

        Age = age;

        Weight = weight;

        BirthDate = DateTime.Parse(birthdate);

    }

    //if ordering by Age from youngest to oldest

    public int CompareToXXX(Person otherPerson)

    {

        if (this.Age > otherPerson.Age)

            return 1;

        else

            return -1;

    }

    //if ordering by BirthDate from most recent down to oldest

    public int CompareTo(Person otherPerson)

    {

            if (DateTime.Compare(this.BirthDate, otherPerson.BirthDate) > 0)

            {

                //Means this DateTime is later than the Other one,

                //or in other words, this DateTime is more recent than the other one.

                //As a result, since we want reverse chronological order,

                //that is, from most recent date, down to oldest date,

                //we want "this" item to appear earlier in the sorted list.

                //For that, we return negative.

                return -1;

            }

            else

            {

                return 1;

            }

    }

​

    public override string ToString()

    {

        return "Name=[ " + Name + " ]  Age=[ "  + Age.ToString() + " ]  Weight=[ " + Weight.ToString() + " ]  BirthDate=[ " + BirthDate.ToString("yyyy-MM-dd") + " ]";

    }

}

//when ordering by BirthDate in reverse chrono order, from most recent, down to oldest:

/*

Name=[ Billy ]  Age=[ 19 ]  Weight=[ 190 ]  BirthDate=[ 1984-12-11 ]

Name=[ Debbie ]  Age=[ 19 ]  Weight=[ 210 ]  BirthDate=[ 1984-12-11 ]

Name=[ Adam ]  Age=[ 18 ]  Weight=[ 180 ]  BirthDate=[ 1960-01-05 ]

Name=[ Cristina ]  Age=[ 16 ]  Weight=[ 260 ]  BirthDate=[ 1955-07-04 ]

*/

​