protected void RegisterUser(object sender, EventArgs e)
    {
        int userId = 0;
        string constr = ("Data Source = 'PAULO'; Initial Catalog=ShoppingCartDB;Integrated Security =True");
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand("Insert_User"))
            {
                using (SqlDataAdapter sda = new SqlDataAdapter())
                {
                    cmd.CommandType = CommandType.StoredProcedure;
                    cmd.Parameters.AddWithValue("@Username", txtUser.Text.Trim());
                    cmd.Parameters.AddWithValue("@Firstname", txtFN.Text.Trim());
                    cmd.Parameters.AddWithValue("@Lastname", txtLN.Text.Trim());
                    cmd.Parameters.AddWithValue("@Email", txtEmail.Text.Trim());
                    cmd.Parameters.AddWithValue("@Password", BusinessLayer.ShoppingCart.CreateSHAHash (txtPW.Text));
                    cmd.Parameters.AddWithValue("@CustomerType", RadioButtonList1.SelectedItem.ToString());
                    cmd.Parameters.AddWithValue("@Street", txtStreet.Text.Trim());
                    cmd.Parameters.AddWithValue("@Province", dropdownProvince.SelectedItem.ToString());
                    cmd.Parameters.AddWithValue("@City", DropDownCity.SelectedItem.ToString());
                    cmd.Parameters.AddWithValue("@Barangay", DropDownBarangay.SelectedItem.ToString());
                    cmd.Parameters.AddWithValue("@Zip", txtZip.Text.Trim());
                    cmd.Parameters.AddWithValue("@ContactNumber", txtContact.Text.Trim());
                    cmd.Connection = con;
                    con.Open();
                    userId = Convert.ToInt32(cmd.ExecuteScalar());
                    con.Close();
                }
            }
            string message = string.Empty;
            switch (userId)
            {
                case -1:
                    message = "Username already exists.\nPlease choose a different username.";
                    break;
                case -2:
                    message = "Supplied email address has already been used.";
                    break;
                default:
                    message = "Registration successful. Activation email has been sent.";
                    SendActivationEmail(userId);
                    break;
            }
            ClientScript.RegisterStartupScript(GetType(), "alert", "alert('" + message + "');", true);
        }
    }

    private void SendActivationEmail(int userId)
    {
        string constr = ("Data Source = 'PAULO'; Initial Catalog=ShoppingCartDB;Integrated Security =True");
        string activationCode = Guid.NewGuid().ToString();
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand("INSERT INTO UserActivation VALUES(@UserId, @ActivationCode)"))
            {
                using (SqlDataAdapter sda = new SqlDataAdapter())
                {
                    cmd.CommandType = CommandType.Text;
                    cmd.Parameters.AddWithValue("@UserId", userId);
                    cmd.Parameters.AddWithValue("@ActivationCode", activationCode);
                    cmd.Connection = con;
                    con.Open();
                    cmd.ExecuteNonQuery();
                    con.Close();
                }
            }
        }
        using (MailMessage mm = new MailMessage("sender@gmail.com", txtEmail.Text))
        {
            mm.Subject = "Account Activation";
            string body = "Hello " + txtUser.Text.Trim() + ",";
            body += "<br /><br />Please click the following link to activate your account";
            body += "<br /><a href = '" + Request.Url.AbsoluteUri.Replace("trial.aspx", "CS_Activation.aspx?ActivationCode=" + activationCode) + "'>Click here to activate your account.</a>";
            body += "<br /><br />Thanks";
            mm.Body = body;
            mm.IsBodyHtml = true;
            SmtpClient smtp = new SmtpClient();
            smtp.Host = "smtp.gmail.com";
            smtp.EnableSsl = true;
            NetworkCredential NetworkCred = new NetworkCredential();
            NetworkCred.UserName = ConfigurationManager.AppSettings["UserName"];
            NetworkCred.Password = ConfigurationManager.AppSettings["Password"];
            smtp.UseDefaultCredentials = true;
            smtp.Credentials = NetworkCred;
            smtp.Port = 587;
            smtp.Send(mm);
        }
    }
}

protected void btn_Login_Click(object sender, EventArgs e)
    {
        SqlConnection conn = new SqlConnection("Data Source = 'PAULO'; Initial Catalog=ShoppingCartDB;Integrated Security =True");
        conn.Open();
        string checkuser = "select count(*) from UserData where Username = '" + txtUser.Text + "'";
        SqlCommand scm = new SqlCommand(checkuser, conn);
        int temp = Convert.ToInt32(scm.ExecuteScalar().ToString());
        conn.Close();
        if (temp == 1)
        {
            conn.Open();
            string checkPassword = "select Password from UserData where Username ='" + txtUser.Text + "'";
            SqlCommand passCom = new SqlCommand(checkPassword, conn);
            string password = passCom.ExecuteScalar().ToString();
            if (password == BusinessLayer.ShoppingCart.CreateSHAHash(txtPassword.Text))
            {
                Session["New"] = txtUser.Text;
                Response.Write("<script>alert('Logged In')</script>");
                Response.Redirect("OrderNow.aspx");
            }
            else
            {
                lblcrederror.Text = ("Credentials dont match");
            }

        }
        else
        {
            lblcrederror.Text = ("Credentials dont match");
        }
    }
}