Listbox data in database

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Windows.Forms;
using System.Data;
using System.Data.SqlClient;
 
namespace test
{
public partial class MainForm : Form
{
  public MainForm()
  {
      InitializeComponent();
  }
 
  void Button1Click(object sender, EventArgs e)
  {
     SqlConnection conn = new SqlConnection(@"User ID=username; Password=pass; 
                    Initial Catalog=databasename; data source=localhost");
     SqlCommand cmd = conn.CreateCommand();
     foreach(ListItem i in listBox1.SelectedItem)
           {
               cmd.CommandText = "INSERT INTO TableName (columnName) VALUES('"+i.Text)+"')";
               cmd.ExecuteNonQuery();
           }
     conn.Close();
  }
}