How to convert number to words in visual studio 2008

Question

Can anyone teach me how to convert numbers to words? For example:

18,000.00

In words:

eighteen thousand

Hope anyone can help. I am using Visual Studio 2008 professional edition.

Answer 1

High level algorithm:

Break the number into three-digit groups
For each group {
    if value > 0 {
        Compute string translation
        output string + group identifier (eg. million, thousand, etc)
    }
}

The three-digit translation step would need to examine the hundreds digit and out it's string equivalent + " hundred and " if it's greater than 0. The remaining two digits could be used to index into a string array if < 20, or handled separately to index string arrays for each digit.

Answer 2

Here is the logic developed by Justin Rogers:

using System;

public class NumberToEnglish {
    private static string[] onesMapping = 
        new string[] {
            "Zero", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight",
            "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen",
            "Sixteen", "Seventeen", "Eighteen", "Nineteen"
        };
    private static string[] tensMapping =
        new string[] {
            "Twenty", "Thirty", "Forty", "Fifty", "Sixty", 
            "Seventy", "Eighty", "Ninety"
        };
    private static string[] groupMapping =
        new string[] {
            "Hundred", "Thousand", "Million", "Billion", "Trillion"
        };

    private static void Main(string[] args) {
        Console.WriteLine(EnglishFromNumber(long.Parse(args[0])));
    }

    private static string EnglishFromNumber(int number) {
        return EnglishFromNumber((long) number);
    }

    private static string EnglishFromNumber(long number) {
        if ( number == 0 ) {
            return onesMapping[number];
        }

        string sign = "Positive";
        if ( number < 0 ) {
            sign = "Negative";
            number = Math.Abs(number);
        }

        string retVal = null;
        int group = 0;
        while(number > 0) {
            int numberToProcess = (int) (number % 1000);
            number = number / 1000;

            string groupDescription = ProcessGroup(numberToProcess);
            if ( groupDescription != null ) {
                if ( group > 0 ) {
                    retVal = groupMapping[group] + " " + retVal;
                }
                retVal = groupDescription + " " + retVal;
            }

            group++;
        }

        return sign + " " + retVal;
    }

    private static string ProcessGroup(int number) {
        int tens = number % 100;
        int hundreds = number / 100;

        string retVal = null;
        if ( hundreds > 0 ) {
            retVal = onesMapping[hundreds] + " " + groupMapping[0];
        }
        if ( tens > 0 ) {
            if ( tens < 20 ) {
                retVal += ((retVal != null) ? " " : "") + onesMapping[tens];
            } else {
                int ones = tens % 10;
                tens = (tens / 10) - 2; // 20's offset

                retVal += ((retVal != null) ? " " : "") + tensMapping[tens];

                if ( ones > 0 ) {
                    retVal += ((retVal != null) ? " " : "") + onesMapping[ones];
                }
            }
        }

        return retVal;
    }
}