Here's my code...

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;

namespace Hello
{
///

/// Summary description for WebForm1.
///

public class Default : System.Web.UI.Page
{
protected System.Web.UI.WebControls.Label Label1;
protected System.Web.UI.WebControls.Button Button1;
protected System.Web.UI.WebControls.TextBox TextBox1;

private void Page_Load(object sender, System.EventArgs e)
{
if (Session["helloname"] == null)
Session.Add("helloname","");

TextBox1.Text = Session["helloname"].ToString();
}

#region Web Form Designer generated code
override protected void OnInit(EventArgs e)
{
//
// CODEGEN: This call is required by the ASP.NET Web Form Designer.
//
InitializeComponent();
base.OnInit(e);
}

///

/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
///

private void InitializeComponent()
{ this.TextBox1.AutoPostBack = true;
this.TextBox1.TextChanged += new System.EventHandler(this.TextBox1_TextChanged);
this.Button1.Click += new System.EventHandler(this.Button1_Click);
this.Load += new System.EventHandler(this.Page_Load);
}
#endregion

private void Button1_Click(object sender, System.EventArgs e)
{
Server.Transfer("Default_form_ASPX_source.aspx");
}

private void TextBox1_TextChanged(object sender, System.EventArgs e)
{
Session["helloname"] = this.TextBox1.Text;
Server.Transfer("Hello.aspx");

}


}
}