listbox

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 WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        Form2 newform;
        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            int a1, an, d, n, sn;
            a1 = int.Parse(textBox1.Text);
            d = int.Parse(textBox2.Text);
            n = int.Parse(textBox3.Text);
            an = a1 + (n - 1) * d;
            sn = n * (a1 + an) / 2;
            textBox4.Text = "" + an;
            textBox5.Text = "" + sn;
        }
        private void Form1_Load(object sender, EventArgs e)
        {
        }
        private void button2_Click(object sender, EventArgs e)
        {
            newform = new Form2();
            newform.Show();
        }
    }
--------------------------------------------------------
            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 WindowsFormsApplication1
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
         listBox1.Items.Add("1*1= 1 1*2= 2 1*3= 3 1*4= 4 1*5= 5 1*6= 6 1*7= 7 1*8= 8 1*9= 9");
            listBox1.Items.Add("2*1= 2 2*2= 4 2*3= 6 2*4= 8 2*5=10 2*6=12 2*7=14 2*8=16 2*9=18");
            listBox1.Items.Add("3*1= 2 3*2= 6 3*3= 9 3*4=12 3*5=15 3*6=18 3*7=21 3*8=24 3*9=27");
            listBox1.Items.Add("4*1= 4 4*2= 8 4*3=12 4*4=16 4*5=20 4*6=24 4*7=28 4*8=32 4*9=36");
            listBox1.Items.Add("5*1= 5 5*2=10 5*3=15 5*4=20 5*5=25 5*6=30 5*7=35 5*8=40 5*9=45");
            listBox1.Items.Add("6*1= 6 6*2=12 6*3=18 6*4=24 6*5=30 6*6=36 6*7=42 6*8=48 6*9=54");
            listBox1.Items.Add("7*1= 7 7*2=14 7*3=21 7*4=28 7*5=35 7*6=42 7*7=49 7*8=56 7*9=63");
            listBox1.Items.Add("8*1= 8 8*2=16 8*3=24 8*4=32 8*5=40 8*6=48 8