如何从c#表单中调用c#类

这是我的类:

using System;
using System.Collections.Generic;
using System.Text;
namespace Num2Wrd
{
public class NumberToEnglish
{
    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") : ("");
        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/Rupees
                    endStr = (isCurrency) ? ("Rupees " + endStr) : ("");
                    pointStr = translateRupees(points);
                }
            }
            val = String.Format("{0} {1}{2} {3}", translateWholeNumber(wholeNo).Trim(), andStr, pointStr, endStr);
        }
        catch
        {
            ;
        }
        return val;
    }
    private String translateWholeNumber(String number)
    {
        string word = "";
        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
                        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 = " and " + word.Trim();
                }
                //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 translateRupees(String Rupees)
    {
        String cts = "", digit = "", engOne = "";
        for (int i = 0; i < Rupees.Length; i++)
        {
            digit = Rupees[i].ToString();
            if (digit.Equals("0"))
            {
                engOne = "Zero";
            }
            else
            {
                engOne = ones(digit);
            }
            cts += " " + engOne;
        }
        return cts;
    }
}
}

表单包含两个文本框(textBox1和textBox2)和一个按钮(button1)。我想在textBox1中输入一个数字，然后点击按钮。在textBox1中以数字形式输入的金额必须转换为文本并显示在textbox2中。转换函数在上面的c#类文件中。我是一个新学生。谁能帮我解决这个问题?

 public partial class Form1 : Form
    {
        NumberToEnglish neObj = new NumberToEnglish();
        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            textBox2.Text = neObj.changeCurrencyToWords(Convert.ToDouble(textBox1.Text));
        }
    }

 public partial class Form1 : Form
    {
        NumberToEnglish Obj = new NumberToEnglish();
        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            textBox2.Text = Obj.changeCurrencyToWords(textBox1.Text);//As your method accept a string..
        }
    }