Solve The code problem

i am making a windows form application to insert data. i used service based database for storing the data.
i am using following code.

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;
using System.IO;

namespace App4
{
    public partial class Form1 : Form
    {
        SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\v11.0;AttachDbFilename=|DataDirectory|\db.mdf;Integrated Security=True");
       
        SqlDataAdapter ad = new SqlDataAdapter();
        DataSet ds = new DataSet();

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            con.Open();
            ad.InsertCommand = new SqlCommand("insert into data (name,age,phone) values ('" + textBox1.Text + "','" + textBox2.Text + "','" + textBox3.Text + "')", con);
            ad.InsertCommand.ExecuteNonQuery();
            ad.InsertCommand.Dispose();
            con.Close();
           

            ad.SelectCommand = new SqlCommand("select * from data", con);
            con.Open();
            ad.Fill(ds);
            con.Close();
        }
    }
}




in this code insert command executing and ds is also filling with the last entered data. but main problem is that this data is not showing into the data table.
why?????


please give the sollution for this problem.