using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        // Assignment 1

        Console.WriteLine("Assignment 1");

        List<Vehicle> list = new List<Vehicle>

        {

            new Vehicle {Price = 5},

            new Vehicle {Price = 2},

            new Vehicle {Price = 9},

            new Vehicle {Price = 1}

        };

​

        list.Sort();

​

        foreach (var vehicle in list)

        {

            Console.WriteLine(vehicle.Price);

        }

​

        // Assignment 2

        Console.WriteLine("\nAssignment 2");

        Vehicle first = new Vehicle { Price = 2 };

        Vehicle second = new Vehicle { Price = 2 };

​

        Console.WriteLine(first.Equals(second));

​

        // Assignment 3

        Console.WriteLine("\nAssignment 3");

        VehicleCollection collection = new VehicleCollection();

        collection.Add(new Vehicle { Price = 5} );

        collection.Add(new Vehicle { Price = 2} );

        collection.Add(null);

        collection.Add(new Vehicle { Price = 9} );

        collection.Add(new Vehicle { Price = 1} );

​

        foreach (Vehicle vehicle in collection)

        {

            Console.WriteLine(vehicle.Price);

        }

    }

}

​

class VehicleCollection : IEnumerable<Vehicle>

{

    List<Vehicle> list;

    public VehicleCollection()

    {

        list = new List<Vehicle>();

    }

    public void Add(Vehicle vehicle)

    {

        if (vehicle != null)

        {

            list.Add(vehicle);

        }

    }

    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()

    {

        return this.list.GetEnumerator();

    }

    IEnumerator<Vehicle> IEnumerable<Vehicle>.GetEnumerator()

    {

        return this.list.GetEnumerator();

    }

}

​

class Vehicle : IComparable<Vehicle>

{

    public int Price;

    public int CompareTo(Vehicle other)

    {

        return this.Price.CompareTo(other.Price);

    }

    public override bool Equals(object obj)

    {

        if (obj == null)

        {

            return false;

        }

        if (!(obj is Vehicle))

        {

            return false;

        }

        return (this.Price == ((Vehicle) obj).Price);

    }

    public override int GetHashCode()

    {

        return this.Price.GetHashCode();

    }

}