problem in uploading attachment

I have also work on a job portal and use to send resume on mail like as
on applybutton click


 MailMessage mail = new MailMessage();

  mail.To.Add(lblempemail.Text.TrimEnd(',')); 
  mail.From = new MailAddress("emailid"); 
  mail.IsBodyHtml = true;
  mail.Body = "html body code";

  DataSet objds3 = new DataSet();
  string resume = "select resumes from newregistration where email='" + Session["userid"].ToString() + "'";
  objds3 = objdal.FillDataSet(CommandType.Text, resume);
  // if (dslog.Tables[0].Rows.Count > 0)
  {

  mail.Attachments.Add(new Attachment(Server.MapPath(objds3.Tables[0].Rows[0]["resumes"].ToString())));
//get resume path
  }
 
  SmtpClient smtp = new SmtpClient();
  smtp.Host = "your host";
  smtp.Port = 25;
  smtp.EnableSsl = false;
  smtp.Credentials = new System.Net.NetworkCredential("youremail", "password");

  smtp.Send(mail);

http://www.aspnettutorials.com/tutorials/email/email-attach-aspnet2-csharp/