ListBox.cs

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;
using System.Data.SqlClient;

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

        private void Form1_Load(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection(@"Data Source=LAPTOP-3G9KFH97; Initial Catalog=master; Integrated Security=true");
            SqlCommand cmd = new SqlCommand("select * from emp",con);

            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();

            con.Open();
            da.Fill(dt);

            lb.DataSource = dt;
            lb.DisplayMember = "name";
            lb.ValueMember = "id";
        }
    }
}