adding Records in grid on Button click and maintain state

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

public partial class staticgridview : System.Web.UI.Page
{

DataTable dt1 = new DataTable();
private void gridVIEWData()
{

dt1.Columns.Add("Name", typeof(string));
dt1.Columns.Add("Age", typeof(int));
Session["dtInSession"] = dt1;

}

protected void Page_Load(object sender, EventArgs e)
{

if (!IsPostBack)
{

gridVIEWData();

GridView1.DataSource = dt1;

GridView1.DataBind();

}

}









protected void Button1_Click(object sender, EventArgs e)
{



if (Session["dtInSession"] != null)
dt1 = (DataTable)Session["dtInSession"]; //Getting datatable from session


DataRow dr = dt1.NewRow();
dr["Name"] = TextBox1.Text;
dr["Age"] = TextBox2.Text;


dt1.Rows.Add(dr);

Session["dtInSession"] = dt1; //Saving Datatable To Session
GridView1.DataSource = dt1;

GridView1.DataBind();



}



}