Paging to show the data of table in GRID VIEW.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data;

public partial class reg3 : System.Web.UI.Page
{
    SqlConnection con;
    SqlCommand cmd;
    SqlDataReader dr;

    protected void Page_Load(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection(@"data source=RAJAT\SQLEXPRESS;initial catalog= master;integrated security=sspi;");
        con.Open();
     
        SqlDataAdapter da = new SqlDataAdapter("select * from registration", con);
        DataSet ds = new DataSet();
        da.Fill(ds);
        GridView1.DataSource = ds;
        GridView1.DataBind();
       
        con.Close();
    }
    protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
       
        GridView1.PageIndex = e.NewPageIndex;
        SqlConnection con = new SqlConnection(@"data source=RAJAT\SQLEXPRESS;initial catalog= master;integrated security=sspi;");
        con.Open();
       
        SqlDataAdapter da = new SqlDataAdapter("select * from registration", con);
        DataSet ds = new DataSet();
        da.Fill(ds);
        GridView1.DataSource = ds;
        GridView1.DataBind();
       
        con.Close();
    }
}