form1.cs

Visual C#2005程序设计教程

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

namespace WinAppTest5_1筛选素数
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (txtNum.Text == "")
            {
                MessageBox.Show("请输入一个正整数", "提示",
                    System.Windows.Forms.MessageBoxButtons.OK,
                    System.Windows.Forms.MessageBoxIcon.Information);
                return;
            }
            int n = int.Parse(txtNum.Text);
            int a = 1;
            for(int i=3;i<=n;i++)
            {
                a = 1;
                for(int j = 2;j < i;j++)
                    if(i % j == 0)
                    {
                        a = 0;
                        break;
                    }
                if(a==1)
                    lstPrime.Items.Add(i);
            }
        }
    }
}