Not work Convert Number into Word in C# window : I try to Convert Number into Word in C# windows. I apply Code is ::-


namespace Num2Text
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            textBox2.Text = changeToWords(textBox1.Text, false);
        }
        public String changeNumericToWords(double numb)
        {
            String num = numb.ToString();
            return changeToWords(num, false);
        }
        public String changeCurrencyToWords(String numb)
        {
            return changeToWords(numb, true);
        }
        public String changeNumericToWords(String numb)
        {
            return changeToWords(numb, false);
        }
        public String changeCurrencyToWords(double numb)
        {
            return changeToWords(numb.ToString(), true);
        }
        private String changeToWords(String numb, bool isCurrency)
        {
            String val = "", wholeNo = numb, points = "", andStr = "", pointStr = "";
            String endStr = (isCurrency) ? ("Only") : ("Only"); //-- Only-- 
            try
            {
                int decimalPlace = numb.IndexOf(".");
                if (decimalPlace > 0)
                {
                    wholeNo = numb.Substring(0, decimalPlace);
                    points = numb.Substring(decimalPlace + 1);
                    if (Convert.ToInt32(points) > 0)
                    {
                        andStr = (isCurrency) ? ("and") : ("Point");// just to separate whole numbers from points/cents 
                        endStr = (isCurrency) ? ("Cents " + endStr) : ("Only"); //--Paisa Only-- 
                        pointStr = translateCents(points);
                    }
                }
                val = String.Format("{0} {1}{2} {3}", translateWholeNumber(wholeNo).Trim(), andStr, pointStr, endStr);
            }
            catch { ;}
            return val;
        }
        private String translateWholeNumber(String number)
        {
            string word = " "; //--Taka-- 
            try
            {
                bool beginsZero = false;//tests for 0XX 
                bool isDone = false;//test if already translated 
                double dblAmt = (Convert.ToDouble(number));
                //if ((dblAmt > 0) && number.StartsWith("0")) 
                if (dblAmt > 0)
                {//test for zero or digit zero in a nuemric 
                    beginsZero = number.StartsWith("0");
                    int numDigits = number.Length;
                    int pos = 0;//store digit grouping 
                    String place = " ";//digit grouping name:hundres,thousand,etc... 
                    switch (numDigits)
                    {
                        case 1://ones' range 
                            word = ones(number);
                            isDone = true;
                            break;
                        case 2://tens' range 
                            word = tens(number);
                            isDone = true;
                            break;
                        case 3://hundreds' range 
                            pos = (numDigits % 3) + 1;
                            place = " Hundred ";
                            break;
                        case 4://thousands' range 
                        case 5:
                        case 6:
                            pos = (numDigits % 4) + 1;//
                            place = " Thousand ";
                            break;
                        case 7://millions' range 
                        case 8:
                        case 9:
                            pos = (numDigits % 7) + 1;
                            place = " Million ";
                            break;
                        case 10://Billions's range 
                            case 11:
                            case 12:
                            pos = (numDigits % 10) + 1;
                            place = " Billion ";
                            break;
                        //add extra case options for anything above Billion... 
                        default:
                            isDone = true;
                            break;
                    }
                    if (!isDone)
                    {//if transalation is not done, continue...(Recursion comes in now!!) 
                        word = translateWholeNumber(number.Substring(0, pos)) + place + translateWholeNumber(number.Substring(pos));
                        //check for trailing zeros 
                        if (beginsZero) word = "  " + word.Trim();//-----"and"---
                    }
                    //ignore digit grouping names 
                    if (word.Trim().Equals(place.Trim())) word = "";
                }
            }
            catch { ;}
            return word.Trim();
        }
        private String tens(String digit)
        {
            int digt = Convert.ToInt32(digit);
            String name = null;
            switch (digt)
            {
                case 10:
                    name = "Ten";
                    break;
                case 11:
                    name = "Eleven";
                    break;
                case 12:
                    name = "Twelve";
                    break;
                case 13:
                    name = "Thirteen";
                    break;
                case 14:
                    name = "Fourteen";
                    break;
                case 15:
                    name = "Fifteen";
                    break;
                case 16:
                    name = "Sixteen";
                    break;
                case 17:
                    name = "Seventeen";
                    break;
                case 18:
                    name = "Eighteen";
                    break;
                case 19:
                    name = "Nineteen";
                    break;
                case 20:
                    name = "Twenty";
                    break;
                case 30:
                    name = "Thirty";
                    break;
                case 40:
                    name = "Fourty";
                    break;
                case 50:
                    name = "Fifty";
                    break;
                case 60:
                    name = "Sixty";
                    break;
                case 70:
                    name = "Seventy";
                    break;
                case 80:
                    name = "Eighty";
                    break;
                case 90:
                    name = "Ninety";
                    break;
                default:
                    if (digt > 0)
                    {
                        name = tens(digit.Substring(0, 1) + "0") + " " + ones(digit.Substring(1));
                    }
                    break;
            }
            return name;
        }
        private String ones(String digit)
        {
            int digt = Convert.ToInt32(digit);
            String name = "";
            switch (digt)
            {
                case 1:
                    name = "One";
                    break;
                case 2:
                    name = "Two";
                    break;
                case 3:
                    name = "Three";
                    break;
                case 4:
                    name = "Four";
                    break;
                case 5:
                    name = "Five";
                    break;
                case 6:
                    name = "Six";
                    break;
                case 7:
                    name = "Seven";
                    break;
                case 8:
                    name = "Eight";
                    break;
                case 9:
                    name = "Nine";
                    break;
            }
            return name;
        }
        private String translateCents(String cents)
        {
            String cts = "", digit = "", engOne = "";
            for (int i = 0; i < cents.Length; i++)
            {
                digit = cents[i].ToString();
                if (digit.Equals("0"))
                {
                    engOne = "Zero";
                }
                else
                {
                    engOne = ones(digit);
                }
                cts += " " + engOne;
            }
            return cts;
        } 



[enter image description here][1]

It working to convert (from One to Billion). But there is a error ,when Hundred Position is null. <<<Like as Skin Shot >>> 


  [1]: https://i.stack.imgur.com/AT8j0.jpg

what is the right code ?