C# asal sayı bulma

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Text;

using System.Windows.Forms;

namespace WindowsApplication8

{

public partial class Form1 : Form

{

public Form1()

{

InitializeComponent();

}

private void button1_Click(object sender, EventArgs e)

{

int i, a, b, top, j;

a = Convert.ToInt32(textBox1.Text);

b = Convert.ToInt32(textBox2.Text);

for (i = a; i <= b; i++) { top = 0; for (j = 1; j <= i; j++) if (i % j == 0) top = top + 1; if (top == 2) listBox1.Items.Add(Convert.ToString(i)); } } } }