protected void Button1_Click(object sender, EventArgs e)

 {

     string sFileName = System.IO.Path.GetRandomFileName();

     string sGenName = "Friendly.txt";

     //YOu could omit these lines here as you may

     //not want to save the textfile to the server

     //I have just left them here to demonstrate that you could create the text file

     using (System.IO.StreamWriter SW = new System.IO.StreamWriter(

            Server.MapPath("TextFiles/" + sFileName + ".txt")))

     {

         SW.WriteLine(txtText.Text);

         SW.Close();

     }

     System.IO.FileStream fs = null;

     fs = System.IO.File.Open(Server.MapPath("TextFiles/" +

              sFileName + ".txt"), System.IO.FileMode.Open);

     byte[] btFile = new byte[fs.Length];

     fs.Read(btFile, , Convert.ToInt32(fs.Length));

     fs.Close();

     Response.AddHeader("Content-disposition", "attachment; filename=" +

                        sGenName);

     Response.ContentType = "application/octet-stream";

     Response.BinaryWrite(btFile);

     Response.End();

 }