using System;

public class Program

{

    public static void Main()

    {

        string choice;

        double temperature;

        double result;

        Console.WriteLine("Enter C to convert to Celsius or F to convert to Fahrenheit:");

        choice = Console.ReadLine();

​

        if (choice == "C" || choice == "c")

        {

            temperature = GetTemperature("Fahrenheit");

            result = CalculateCelsius(temperature);

            DisplayResult(temperature, "Fahrenheit", result, "Celsius");

            Console.WriteLine("Enter C to convert to Celsius or F to convert to Fahrenheit:");

            choice = Console.ReadLine();

            temperature = GetTemperature("Celsius");

            result = CalculateFahrenheit(temperature);

            DisplayResult(temperature, "Celsius", result, "Fahrenheit");

            Console.WriteLine("Enter C to convert to Celsius or F to convert to Fahrenheit:");

            choice = Console.ReadLine();

            Console.WriteLine("You must enter C to convert to Celsius or F to convert to Fahrenheit.");

            choice = Console.ReadLine();

​

        }

        else if (choice == "F" || choice == "f")

        {

            temperature = GetTemperature("Celsius");

            result = CalculateFahrenheit(temperature);

            DisplayResult(temperature, "Celsius", result, "Fahrenheit");

            Console.WriteLine("Enter C to convert to Celsius or F to convert to Fahrenheit:");

            choice = Console.ReadLine();

            temperature = GetTemperature("Fahrenheit");

            result = CalculateCelsius(temperature);

            DisplayResult(temperature, "Fahrenheit", result, "Celsius");

            Console.WriteLine("Enter C to convert to Celsius or F to convert to Fahrenheit:");

            choice = Console.ReadLine();

            Console.WriteLine("You must enter C to convert to Celsius or F to convert to Fahrenheit.");

            choice = Console.ReadLine();

        }

        else

        {

            Console.WriteLine("You must enter C to convert to Celsius or F to convert to Fahrenheit.");

            choice = Console.ReadLine();

        }

​

        switch(choice)

        {

            case "C":

            case "c":

                temperature = GetTemperature("Fahrenheit");

                result = CalculateCelsius(temperature);

                DisplayResult(temperature, "Fahrenheit", result, "Celsius");

                break;

​

            case "F":

            case "f":

                temperature = GetTemperature("Celsius");

                result = CalculateFahrenheit(temperature);

                DisplayResult(temperature, "Celsius", result, "Fahrenheit");

                break;  

            default:

                Console.WriteLine("You must enter C to convert to Celsius or F to convert to Fahrenheit.");

                break;

        }

    }

​

    private static double GetTemperature(string label)

    {

        string input;

        double temperature;

        Console.WriteLine("Enter " + label + " temperature:");

        input = Console.ReadLine();

        temperature = Convert.ToDouble(input);

​

        return temperature;

    }

​

    private static double CalculateCelsius(double fahrenheit)

    {

        double celsius;

        celsius = (fahrenheit - 32) * 5 / 9;

        return celsius;

    }

​

    private static double CalculateFahrenheit(double celsius)

    {

        double fahrenheit;

        fahrenheit = celsius * 9 / 5 + 32;

        return fahrenheit;

    }

​

    private static void DisplayResult(double fahrenheit, string fromLabel, double celsius, string toLabel)

    {

        Console.WriteLine(fahrenheit.ToString() + "° " + fromLabel + " is " + celsius.ToString() + "° " + toLabel);

    }

}