Trying to set up a menu in the start of program

Question

I am trying to make a simple program that shows a menu in the start, and the user can choose one of the choices on the menu.
Here is what I wrote so far, 
but it's not working for some reason, and I am getting an error called "unreachable code detected" on Console.Write("press Enter to continue");
Halp~~ QQQQ


static void Main(string[] args)
        {
            //menu
            Console.WriteLine("<<Temperature Conversion>>");
            Console.WriteLine("1 - Celsius (C) to Fahrenheit (F)");
            Console.WriteLine("2 - Fahrenheit (F) to Celsius (C)");
            Console.WriteLine("Q - Quit\n");
            Console.Write("Choose (1, 2, or Q):");


            //User input
            string optionChoice = Console.ReadLine();
            optionChoice = Console.ReadLine();






            switch (optionChoice)
            {


                case "1":
                    Console.WriteLine("Celsius (C) to Fahrenheit (F)");
                    break;


                case "2":
                    Console.WriteLine("Fahrenheit (F) to Celsius (C)");
                    break;


                case "Q":
                case "q":
                    Console.WriteLine("Bye bye~");
                    break;


                default:
                    Console.WriteLine("{0} is not valid", optionChoice);
                    break;


                    Console.Write("press Enter to continue"); //Where error is
                    Console.ReadLine();
                    {


                        while (optionChoice != "Q" && optionChoice != "q") ;
                    }


            }