разложение на множители

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Разложение
{
    public partial class Form1 : Form
    {
        public static int len = 0;
        public static int lenf = 0;
        public Form1()
        {
            InitializeComponent();
            len = listBox1.Height;
            lenf = this.Height;
            textBox1.Click += new EventHandler(tb_eventClick);
        }
        private void tb_eventClick(object snd, EventArgs a)
        {
            textBox1.Text = "";
        }

        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                listBox1.Items.Clear();
                listBox1.Height = len;
                this.Height = len + 10;
                decimal a = Convert.ToDecimal(textBox1.Text);
                decimal[] ard = new decimal[1000];
                decimal[] dl = new decimal[1000];
                ard[0] = a;
                for (decimal i = 2, ct = 1, pt = 0; ; )
                {
                    if (a % i == 0)
                    {
                        ard[checked((int)ct++)] = a /= i;
                        dl[checked((int)pt++)] = i;
                    }
                    else i++;
                    if (a == 1)
                    {
                        for (decimal g = 0; g < ct - 1; g++)
                            listBox1.Items.Add(ard[checked((int)g)].ToString() + "," + dl[checked((int)g)].ToString());
                        listBox1.Items.Add(a.ToString());
                        break;
                    }
                }
                listBox1.Height += 13 * listBox1.Items.Count;
                this.Height += listBox1.Height + 40;
            }
            catch (OverflowException)
            {
                MessageBox.Show(this, "Слишком большое число", "Ошибка", MessageBoxButtons.OK);
            }
            catch (Exception)
            {
                this.Height = lenf;
                MessageBox.Show(this, "...", "Ошибка", MessageBoxButtons.OK);
            }
        }
    }
}