05.11.NumberAsWords

using System;
/*Write a program that converts a number in the range [0…999] to words,
 * corresponding to the English pronunciation. Examples:
 * numbers  number as words
 * 0    Zero
 * 9    Nine
 * 10   Ten
 * 12   Twelve
 * 19   Nineteen
 * 25   Twenty five
 * 98   Ninety eight
 * 273  Two hundred and seventy three
 * 400  Four hundred
 * 501  Five hundred and one
 * 617  Six hundred and seventeen
 * 711  Seven hundred and eleven
 * 999  Nine hundred and ninety nine */
class NumberAsWords
{
    static void Main()
    {
        int numberA = 0;

        Console.WriteLine("Enter an integer between 0 and 999:");
        do
        {
            if (int.TryParse(Console.ReadLine(), out numberA) && (numberA >= 0) && (numberA <= 999))
            {
                break;
            }
            else
            {
                Console.WriteLine("You have entered an invalid data!");
            }
        } while (true);

        int firstDigit = numberA / 100; //gets first digit of nuber
        int secondDigit = (numberA / 10) % 10;//gets second digit of nuber
        int thirdDigit = numberA - (firstDigit * 100) - (secondDigit * 10); //gets third digit of nuber
        string firstDigitString = "";
        string secondDigitString = "";
        string thirdDigitString = "";
        string caseThereIslessThan20 = "";

        switch (firstDigit) //geting string for the first digit
        {
            case 0: firstDigitString = ""; break;
            case 1: firstDigitString = "One hundred"; break;
            case 2: firstDigitString = "Two hundred"; break;
            case 3: firstDigitString = "Three hundred"; break;
            case 4: firstDigitString = "Four hundred"; break;
            case 5: firstDigitString = "Five hundred"; break;
            case 6: firstDigitString = "Six hundred"; break;
            case 7: firstDigitString = "Seven hundred"; break;
            case 8: firstDigitString = "Eight hundred"; break;
            case 9: firstDigitString = "Nine hundred"; break;
            default: Console.WriteLine("Error occurred!"); break;
        }

        switch (secondDigit) //geting string for the second digit
        {
            case 0: secondDigitString = ""; break;
            case 1: secondDigitString = "Ten"; break;
            case 2: secondDigitString = "Twenty"; break;
            case 3: secondDigitString = "Thirty"; break;
            case 4: secondDigitString = "Fourty"; break;
            case 5: secondDigitString = "Fifty"; break;
            case 6: secondDigitString = "Sixty"; break;
            case 7: secondDigitString = "Seventy"; break;
            case 8: secondDigitString = "Eighty"; break;
            case 9: secondDigitString = "Ninety"; break;
            default: Console.WriteLine("Errorr occurred!"); break;
        }

        switch (thirdDigit) //geting string for the third digit
        {
            case 0: thirdDigitString = ""; break;
            case 1: thirdDigitString = "One"; break;
            case 2: thirdDigitString = "Two"; break;
            case 3: thirdDigitString = "Three"; break;
            case 4: thirdDigitString = "Four"; break;
            case 5: thirdDigitString = "Five"; break;
            case 6: thirdDigitString = "Six"; break;
            case 7: thirdDigitString = "Seven"; break;
            case 8: thirdDigitString = "Eight"; break;
            case 9: thirdDigitString = "Nine"; break;
            default: Console.WriteLine("Errorr occurred!"); break;
        }

        if (secondDigit < 2) //chaks if there is 20 and less in number
        {

            switch (numberA - ((numberA / 100) * 100))
            /*(numberA/100)*100 is NOT equal to numberA (if numberA is int)
             * I when i did the operation had lost the second and the third digit and after that I draw the
             * result from number and I got the second and the third digit */
            {
                case 0: caseThereIslessThan20 = "Zero"; break;
                case 1: caseThereIslessThan20 = "One"; break;
                case 2: caseThereIslessThan20 = "Two"; break;
                case 3: caseThereIslessThan20 = "Three"; break;
                case 4: caseThereIslessThan20 = "Four"; break;
                case 5: caseThereIslessThan20 = "Five"; break;
                case 6: caseThereIslessThan20 = "Six"; break;
                case 7: caseThereIslessThan20 = "Seven"; break;
                case 8: caseThereIslessThan20 = "Eight"; break;
                case 9: caseThereIslessThan20 = "Nine"; break;
                case 10: caseThereIslessThan20 = "Ten"; break;
                case 11: caseThereIslessThan20 = "Eleven"; break;
                case 12: caseThereIslessThan20 = "Twelve"; break;
                case 13: caseThereIslessThan20 = "Thirdtheen"; break;
                case 14: caseThereIslessThan20 = "Fourteen"; break;
                case 15: caseThereIslessThan20 = "Fiveteen"; break;
                case 16: caseThereIslessThan20 = "Sixteen"; break;
                case 17: caseThereIslessThan20 = "Seventeen"; break;
                case 18: caseThereIslessThan20 = "Eightteen"; break;
                case 19: caseThereIslessThan20 = "Nineteen"; break;
                default: Console.WriteLine("Errorr occurred!"); break;
            }
        }

        //printing results for diferent cases
        Console.Clear();
        Console.WriteLine("number\tnumber as words");
        if (firstDigit == 0 && secondDigit < 2)
        {
            Console.WriteLine("{0}\t{1}", numberA, caseThereIslessThan20);
        }
        else if (firstDigit == 0 && secondDigit >= 2)
        {
            Console.WriteLine("{0}\t{1} {2}", numberA, secondDigitString, thirdDigitString.ToLower());
        }
        else if (firstDigit > 0 && secondDigit < 2)
        {
            if (secondDigit == 0 && thirdDigit == 0)
            {
                Console.WriteLine("{0}\t{1}", numberA, firstDigitString);
            }
            else
            {
                Console.WriteLine("{0}\t{1} and {2}", numberA, firstDigitString, caseThereIslessThan20.ToLower());
            }
        }
        else if (firstDigit > 0 && secondDigit >= 2)
        {
            Console.WriteLine("{0}\t{1} and {2} {3}", numberA, firstDigitString, secondDigitString.ToLower(), thirdDigitString.ToLower());
        }
        else
        {
            Console.WriteLine("I can not belive that is happening!");
        }
    }
}