Temperature

// This program asks the user to select Fahrenheit or Celsius conversion
// and input a given temperature. Then the program converts the given 
// temperature and displays the result.
//
// References:
//     https://www.mathsisfun.com/temperature-conversion.html
//     https://en.wikibooks.org/wiki/C_Sharp_Programming

using System;

public class MainClass
{
    public static void Main(String[] args)
    {
        // main could either be an if-else structure or a switch-case structure

        string choice;
        double temperature;
        double result;
                
        Console.WriteLine("Enter F to convert to Fahrenheit or C to convert to Celsius:");
        choice = Console.ReadLine();

        // if-else approach
        if (choice == "C" || choice == "c")
        {
            temperature = GetTemperature("Fahrenheit");
            result = CalculateCelsius(temperature);
            DisplayResult(temperature, "Fahrenheit", result, "Celsius");
        }
        else if (choice == "F" || choice == "f")
        {
            temperature = GetTemperature("Celsius");
            result = CalculateFahrenheit(temperature);
            DisplayResult(temperature, "Celsius", result, "Fahrenheit");
        }
        else
        {
            Console.WriteLine("You must enter C to convert to Celsius or F to convert to Fahrenheit!");
        }

        // switch-case approach
        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);
    }
}

Enter C to convert to Celsius or F to convert to Fahrenheit:
 c
Enter Fahrenheit temperature:
 100
100° Fahrenheit is 37.7777777777778° Celsius

Enter C to convert to Celsius or F to convert to Fahrenheit:
 f
Enter Celsius temperature:
 100
100° Celsius is 212° Fahrenheit

Enter C to convert to Celsius or F to convert to Fahrenheit:
 x
You must enter C to convert to Celsius or F to convert to Fahrenheit.

References

• Wikiversity: Computer Programming