Delete a certain rows from database after read read the data

To:
Subject:
Body:
Gmail Email:
Gmail Password:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.IO;

using System.Net;

using System.Net.Mail;

using System.Data;

using System.Data.SqlClient;

public partial class email : System.Web.UI.Page

{

SqlCommand cmd = new SqlCommand();

SqlConnection con = new SqlConnection();

protected void Page_Load(object sender, EventArgs e)

{

con.ConnectionString = @"Data Source=PC\GAMETAIKO;Initial Catalog=login;Integrated Security=True";

}

protected void SendEmail(object sender, EventArgs e)

{

con.Open();

String query = "INSERT INTO cubaan2 (fromSender, toSender, subjectSender, status) VALUES( '" + txtEmail.Text + "', '" + txtTo.Text + "', '" + txtSubject.Text + "', '" + "' ) ";

SqlDataAdapter SDA = new SqlDataAdapter(query, con);

SDA.SelectCommand.ExecuteNonQuery();

con.Close();

using (MailMessage mm = new MailMessage(txtEmail.Text, txtTo.Text))

{

mm.Subject = txtSubject.Text;

mm.Body = txtBody.Text;

SmtpClient smtp = new SmtpClient();

smtp.Host = "smtp.gmail.com";

smtp.EnableSsl = true;

NetworkCredential NetworkCred = new NetworkCredential(txtEmail.Text, txtPassword.Text);

smtp.UseDefaultCredentials = true;

smtp.Credentials = NetworkCred;

smtp.Port = 587;

smtp.Send(mm);

ClientScript.RegisterStartupScript(GetType(), "alert", "alert('Email sent.');", true);

}

}

}