Adding attachment to mail

 Hi
I've written code to send mail with attachment but its giving error im not able to rectify it can any 1 say wat's my mistake?
protected void Button1_Click(object sender, EventArgs e)
    {
        try
        {
            bool flag = true;             
            MailMessage Mail = new MailMessage();
            //SmtpClient smtpc = new SmtpClient("172.16.0.1");
            Mail.To = TextBox1.Text.Trim();
            Mail.From = TextBox2.Text.Trim();
      ...