Entire column of database store in session

using System;
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;
using System.Collections.Generic;
public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {

        DataTable table = new DataTable();
        table.Columns.Add("empname", typeof(string));
        table.Columns.Add("password", typeof(string));
        

        //
        // Here we add five DataRows.
        //
        table.Rows.Add("deva","raj123");
        table.Rows.Add("somu","somu123");
        
    

        //assing datatable values to session Object
        //storing datatable values to Session Object
        Session["sampletable"] = table;

        //Fetching datatable table values from Session Object
        //Reading datatable values from Session Object
        DataTable dt = (DataTable)Session["sampletable"];


        //displaying datatable values to GridView
        GridView1.DataSource = dt;
        GridView1.DataBind();
      
    }

using System.Data;
public partial class StSession : System.Web.UI.Page
{
    DataTable dt = new DataTable();
    DataRow dr;
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            dt.Columns.Add("empname");
            dt.Columns.Add("emppwd");
            Session["dt"] = dt;
        }
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        dt = (DataTable)Session["dt"];
        dr = dt.NewRow();
        dr["empname"] = TextBox1.Text;
        dr["emppwd"] = TextBox2.Text;
        dt.Rows.Add(dr);
        Session["dt"] = dt;
        TextBox1.Text = "";
        TextBox2.Text = "";
    }
    protected void Button2_Click(object sender, EventArgs e)
    {
        GridView1.DataSource = (DataTable)Session["dt"];
        GridView1.DataBind();
    }
}