using System;

public class Invoice 

{

           string partNumber;

            string partDescription;

            int quantity;

            double pricePerItem;

​

            public string PartNumber // get and set accessor for each instance variable

            {

                get { return partNumber; }

                set { partNumber = value; }

            }

​

            public string PartDescription

            {

                get { return partDescription; }

                set { partDescription = value; }

            }

​

            public int Quantity

            {

                get { return quantity; }

                set

                {

                    if (value < 0) value = 0;

                    quantity = value;

                }

            }

​

            public double Price

            {

                get { return pricePerItem; }

                set

                {

                    if (value < 0) value = 0;

                    pricePerItem = value;

                }

            }

​

            public Invoice(string partNumber, string partDescription, int quantity, double pricePerItem)

            {

                PartNumber = partNumber;

                PartDescription = partDescription;

                Quantity = quantity;

                Price = pricePerItem;

            }

​

            public double getInvoiceAmount() // method to get the invoice amount

            {

                return quantity * pricePerItem;

            }

        }

​

        class InvoiceTest

        {

            static void Main()

            {

                Invoice inv = new Invoice("P1", "Widget", 10, 20.5); // testing the capabilities of the invoice class

                double cost = inv.getInvoiceAmount();

                Console.WriteLine("Part {0}, Desc: {1}, Quantity: {2}, Price for each item: {3:C}, Total Cost: {4:C}", inv.PartNumber, inv.PartDescription, inv.Quantity, inv.Price, cost);

                Console.WriteLine();

                Invoice inv2 = new Invoice("P2", "Widget Holder", 2, -1.25);  // testing negative price

                double cost2 = inv2.getInvoiceAmount();

                Console.WriteLine("Part {0}, Desc: {1}, Quantity: {2}, Price for each item: {3:C}, Total Cost: {4:C}", inv2.PartNumber, inv2.PartDescription, inv2.Quantity, inv2.Price, cost2);

                Console.ReadKey();

            }

        }

​

​