当用户输入209,312,414时，程序需要停止

我需要程序在用户输入209,312,414时停止。我的while循环不工作，因为程序在继续。我用了不同的方法，但在最后循环继续，当我输入209,312,414时，它并没有停止。我接受其他的建议。

using System;
        public class program
        {
            public static void Main()
            {
                const double PRICE209 = 12.99, PRICE312 = 16.77, PRICE414 = 109.07;
                double price;
                int stockNum;
                Console.Write("Please enter stock number. ");
                stockNum = Convert.ToInt32(Console.ReadLine());
                while ((stockNum == 209) || (stockNum == 312) || (stockNum == 414))
                {
                    if ((stockNum == 209) || (stockNum == 312) || (stockNum == 414))
                    {
                        if (stockNum == 209)
                        {
                            price = PRICE209;
                            Console.WriteLine("The price for item # {0} is {1}", stockNum, price.ToString("C"));
                        }
                        else if (stockNum == 312)
                        {
                            price = PRICE312;
                            Console.WriteLine("The price for item # {0} is {1}", stockNum, price.ToString("C"));
                        }
                        else if (stockNum == 414)
                        {
                            price = PRICE414;
                            Console.WriteLine("The price for item # {0} is {1}", stockNum, price.ToString("C"));
                        } // end of the else if statement
                    } // end the if statement 
                    Console.Write("Please enter stock number. ");
                    stockNum = Convert.ToInt32(Console.ReadLine());
                }  // end the while loop
                        Console.WriteLine();
                        Console.WriteLine("press <enter> to terminate program");
                        Console.ReadLine();
            }
        }

while ((stockNum != 209) && (stockNum != 312) && (stockNum != 414))