using System;

using System.Collections.Generic;

using System.Collections.ObjectModel;

using System.Linq;

​

public class OrderItem

{

    public readonly int PartNumber;

    public readonly string Description;

    public readonly double UnitPrice;

    private int _quantity = 0;

​

    public OrderItem(int partNumber, string description, int quantity, double unitPrice)

    {

        this.PartNumber = partNumber;

        this.Description = description;

        this.Quantity = quantity;

        this.UnitPrice = unitPrice;

    }

​

    public int Quantity

    {

        get

        {

            return _quantity;

        }

        set

        {

            if (value < 0)

            {

                throw new ArgumentException("Quantity cannot be negative.");

            }

​

            _quantity = value;

        }

    }

​

    public override string ToString()

    {

        return String.Format("{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",

            PartNumber, _quantity, Description, UnitPrice, UnitPrice * _quantity);

    }

}

​

public class Order

{

    private readonly Dictionary<int, OrderItem> _orderItems = new Dictionary<int, OrderItem>();

​

    public IDictionary<int, OrderItem> OrderItems

    {

        get

        {

            return _orderItems;

        }

    }

​

    public void AddRange(IEnumerable<OrderItem> orderItems)

    {

        foreach (var item in orderItems)

        {

            _orderItems.Add(item.PartNumber, item);

        }

    }

​

    public OrderItem FindByPartNumber(int partNumber)

    {

        if (_orderItems.ContainsKey(partNumber))

        {

            return _orderItems[partNumber];

        }

​

        return null;

    }

​

    public IList<OrderItem> FindByDescription(string description)

    {

        return _orderItems.Values.Where(i => i.Description == description).ToArray();

    }

}

​

public class Program

{

    public static void Main()

    {

        var order = new Order();

        order.AddRange(new OrderItem[]

        {

            new OrderItem(110072674, "Widget", 400, 45.17),

            new OrderItem(110072675, "Sprocket", 27, 5.3),

            new OrderItem(101030411, "Motor", 10, 237.5),

            new OrderItem(110072684, "Gear", 175, 5.17)

        });

​

        Display("Order #1", order);

​

        if (order.FindByPartNumber(111033401) == null)

        {

            Console.WriteLine("Order #1 doesn't have #111033401 item.\n");

        }

​

        order.AddRange(new OrderItem[]

        {

            new OrderItem(111033401, "Nut", 10, .5),

            new OrderItem(127700026, "Crank", 27, 5.98)

        });

​

        Display("Order #2", order);

​

        var list = order.FindByDescription("Crank");

        if (list.Count > 0)

        {            

            double itemPrice = list[0].Quantity * list[0].UnitPrice;

            Console.WriteLine("Order #2 has \"Crank\" item - price is {0:###,###.00}$.", itemPrice);

        }

​

        Console.ReadLine();

    }

​

    private static void Display(string title, Order order)

    {

        ICollection<OrderItem> values = order.OrderItems.Values;

​

        Console.WriteLine(title);

        foreach (var item in values)

        {

            Console.WriteLine(item);

        }

        Console.WriteLine();

    }

}