Object reference not set to an instance of an object.

See more:

C#

ASP.NET

first form.......

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
public partial class Default2 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void btnsubmit_Click(object sender, EventArgs e)
    {
        if (IsPostBack)
        {
            Response.Write("you have sucessfully registred...!!!");
        }



    }

    protected void btnsubmit_Click1(object sender, EventArgs e)
    {

        Session["DEMO_SESSION"] = txtname.Text;
        Response.Redirect("default3.aspx");
        Session["DEMO_SESSION1"] = txtpwd.Text;
        Response.Redirect("default3.aspx");
        Session["DEMO_SESSION2"] = txtpassword.Text;
        Response.Redirect("default3.aspx");
        Session["DEMO_SESSION3"] = txtadd.Text;
        Response.Redirect("default3.aspx");
        Session["DEMO_SESSION4"] = txtfull.Text;
        Response.Redirect("default3.aspx");
        Session["DEMO_SESSION5"] = DropDownList1.SelectedIndex;
        Response.Redirect("default3.aspx");


    }
    }

second form......

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

public partial class Default3 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

        TextBox1.Text = Session["DEMO_SESSION"].ToString();
        TextBox2.Text = Session["DEMO_SESSION1"].ToString();
        TextBox3.Text = Session["DEMO_SESSION2"].ToString();
        TextBox4.Text = Session["DEMO_SESSION3"].ToString();
        TextBox5.Text = Session["DEMO_SESSION4"].ToString();
        TextBox6.Text = Session["DEMO_SESSION5"].ToString();



    }
}

error.....
Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

Line 18:
Line 19: TextBox1.Text = Session["DEMO_SESSION"].ToString();
Line 20: TextBox2.Text = Session["DEMO_SESSION1"].ToString();
Line 21: TextBox3.Text = Session["DEMO_SESSION2"].ToString();
Line 22: TextBox4.Text = Session["DEMO_SESSION3"].ToString();