ListBox

디자인

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

namespace _025_ListBox
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void listBox2_SelectedIndexChanged(object sender, EventArgs e)
        {
            ListBox l = sender as ListBox;
            txt_Sldex2.Text = (l.SelectedIndex+1).ToString();
            txt_Sitem2.Text = l.SelectedItem.ToString();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            listBox2.Items.Add("오클랜드(뉴질랜드)");
            listBox2.Items.Add("오사카(일본)");
            listBox2.Items.Add("아델레이드(호주)");
            listBox2.Items.Add("웰링턴(뉴질랜드)");
            listBox2.Items.Add("도쿄(일본)");
            listBox2.Items.Add("퍼스(호주)");
            listBox2.Items.Add("취리히(스위스)");
            listBox2.Items.Add("제네바(스위스)");
            listBox2.Items.Add("멜버른(호주)");
            listBox2.Items.Add("브리즈번(호주)");
            List<string> happines = new List<string>()
            {
                "핀란드","덴마크","아이슬란드","스위스","네덜란드","룩셈부르크","스웨덴","노르웨이","이스라엘","뉴질랜드"
            };
            listBox3.DataSource = happines;
        }

        private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            //ListBox l =(ListBox)sender;
            ListBox l = sender as ListBox;
            txt_Sldex1.Text = (l.SelectedIndex + 1).ToString();
            txt_Sitem1.Text = l.SelectedItem.ToString();
        }

        private void listBox3_SelectedIndexChanged(object sender, EventArgs e)
        {
            ListBox l = sender as ListBox;
            txt_Sldex3.Text = (l.SelectedIndex + 1).ToString();
            txt_Sitem3.Text = l.SelectedItem.ToString();
        }
    }
}

 listBox3.DataSource = happines; 3번째 리스트 박스에 문자열로 추가

실행결과