DataGridView data editing

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

namespace updategrid
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            ds = new DataSet();
        }
        DataSet ds;

        private void button1_Click(object sender, EventArgs e)
        {
            //binding grid to data from database
            SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=phonebook;Integrated Security=True");
            con.Open();
            SqlDataAdapter adp = new SqlDataAdapter("select * from details", con); 
            adp.Fill(ds);
            DataTable dt = ds.Tables[0];
            dataGridView1.DataSource = dt;       
            con.Close();

        }

        private void button2_Click(object sender, EventArgs e)
        {
            //updating values in grid...
            SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=phonebook;Integrated Security=True");
            con.Open();
            SqlDataAdapter adp = new SqlDataAdapter("select * from details", con); 
            SqlCommandBuilder build = new SqlCommandBuilder(adp);
            adp.Update(ds.Tables[0]);
            con.Close();
           
        }
    }
}