multiple mail sending error

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C#

ASP.NET

Hi,
I need to send mail to multiple mailid. the mailid are in database.i tried this by binding the mailid database in gridview.and from gridview in getting the cell value into the textbox.And im using that textbox as my to address of my mail id.in this im getting only the first mailid data in the gridview and the mail send to that mailid its not getting next next mailid data i dnt know why? plz help me

con.Open();
        SqlCommand cmd = new SqlCommand("select * from emailsubscribe", con);
        SqlDataAdapter ada = new SqlDataAdapter(cmd);
        DataTable dt = new DataTable();
        ada.Fill(dt);
        if (dt.Rows.Count > 0)
        {
            for (i = 0; i < dt.Rows.Count; i++)
            {
                TextBox1.Text = GridView1.Rows[0].Cells[1].Text.ToString();
                StringBuilder sb = new StringBuilder();
                MailMessage message = new MailMessage();
                message.From = new MailAddress(TextBox1.Text);
                message.To.Add(new MailAddress(TextBox1.Text));
                message.Subject = "mail subscribe";
                message.Body = "welcome";
                message.IsBodyHtml = true;
                try
                {
                    SmtpClient client = new SmtpClient();
                    client.Host = "smtp.gmail.com";
                    client.Port = 587;
                    client.EnableSsl = true;
                    NetworkCredential credential = new NetworkCredential("id@gmail.com", "password");
                    client.Credentials = credential;
                    client.Send(message);
                }
                catch (Exception ex)
                {
                    Label1.Text = ex.Message;
                }
            }