c# 로또 번호 생성기 소스인데..궁금증이있습니다

using System;

using System.Collections.Generic;

using System.Collections;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Text;

using System.Windows.Forms;

using System.Threading;

using System.Resources;

using System.Reflection;

using System.IO;

namespace Lotto

{

public partial class Form1 : Form

{

ArrayList al;

bool isStarted = false;

private delegate void LabelView1(Label label, string message1);

private delegate void TextBoxView1(TextBox textBox, string message1);

public Form1()

{

InitializeComponent();

return;

}

private void button1_Click(object sender, EventArgs e)

{

if (!this.isStarted)

{

pictureBox1.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.blank.gif"));

pictureBox2.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.blank.gif"));

pictureBox3.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.blank.gif"));

pictureBox4.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.blank.gif"));

pictureBox5.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.blank.gif"));

pictureBox6.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.blank.gif"));

this.label2.Text = "";

this.label3.Text = "";

Thread work = new Thread(doWork);

work.Start();

}

public void doWork()

{

this.isStarted = true;

al = new ArrayList();

Random rd = new Random(DateTime.Now.Millisecond);

for (int i = 0; i < 6; i++)

{

MakeNum(i, rd);

Thread.Sleep(200);

}

al.Sort();

for (int j = 0; j < al.Count; j++)

{

if (j == 0)

pictureBox1.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.ball" + al[j].ToString() + ".gif"));

if (j == 1)

pictureBox2.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.ball" + al[j].ToString() + ".gif"));

if (j == 2)

pictureBox3.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.ball" + al[j].ToString() + ".gif"));

if (j == 3)

pictureBox4.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.ball" + al[j].ToString() + ".gif"));

if (j == 4)

pictureBox5.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.ball" + al[j].ToString() + ".gif"));

if (j == 5)

pictureBox6.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.ball" + al[j].ToString() + ".gif"));

}

this.Invoke(new LabelView1(SetMessage), this.label1, "안상훈대박!!");

this.isStarted = false;

}

public void MakeNum(int i, Random rd)

{

while (true)

{

int n = rd.Next(1, 45);

if (!isNumExists(n))

{

al.Add(n);

int iv = 400;

for (int j = 1; j <= n; j++)

{

if (i == 0)

pictureBox1.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.ball" + j + ".gif"));

if (i == 1)

pictureBox2.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.ball" + j + ".gif"));

if (i == 2)

pictureBox3.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.ball" + j + ".gif"));

if (i == 3)

pictureBox4.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.ball" + j + ".gif"));

if (i == 4)

pictureBox5.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.ball" + j + ".gif"));

if (i == 5)

pictureBox6.Image = new Bitmap(Assembly.GetExecutingAssembly().GetManifestResourceStream("Lotto.ball" + j + ".gif"));

Thread.Sleep(iv/n);

}

break;

}

//this.Invoke(new LabelView1(SetMessageAll), this.label2, i.ToString() +": 중복발생 [" + n + "], 다시 시도\r\n");

}

public bool isNumExists(int num)

{

for (int j = 0; j < this.al.Count; j++)

{

if (this.al[j].Equals(num))

return true;

}

return false;

}

private void SetMessage(Label label, string message)

{

label.Text = ""+message+"";

}

private void SetMessageAll(Label label, string message)

{

label.Text += "" + message + "";

}

private void SetMessageBlank(Label label, string message)

{

label.Text = "" + message + "";

}

private void SetTextBoxAll(TextBox textBox, string message)

{

textBox.Text += "" + message + "";

}

private void Form1_Load(object sender, EventArgs e)

{

//this.ClientSize = new Size(image.Width, image.Height);

//pictureBox1.Image = image;

PictureBox pb = new PictureBox();

pb.Image = image;

pb.Dock = DockStyle.Fill;

this.Controls.Add(pb);

System.Resources.ResourceManager resources = new System.Resources.ResourceManager(typeof(Form1));

this.pictureBox1.Image = (System.Drawing.Image)(resources.GetObject("ball1.gif"));

this.pictureBox1.Name = "pictureBox1";

//pictureBox1.Image = imgNumber;

}

이게 디자이너 폼이 하나 더 있긴 한데 여기서

ArrayList al;

bool isStarted = false;

쓰래드를 무슨 용도로 쓴것인지 궁금합니다 ..

혹시나 아시는분 계신지요 ? ㅠ