private void sendEmailBtn_Click(object sender, RoutedEventArgs e)
        {
            // check if username is correct
            string email;
            User   user = DB.UserLogIn(tbUsername.Text);

            if (user == null)
            {
                SystemSounds.Exclamation.Play();
                MessageBox.Show("There is no user with that username! Try again.");
            }
            else if (string.IsNullOrWhiteSpace(user.Email))
            {
                SystemSounds.Exclamation.Play();
                MessageBox.Show("That username doesn't have an email. Contact support to get your account back.");
            }
            else
            {
                // generate temporary password
                string tempPwd = RandomString(6);

                // send email
                string title   = "Your temporary password - Deniso's Auctions";
                string msgBody = $"Hello {tbUsername.Text},\nThis is your temporary password which you will be able to use to access your account ONLY ONCE and will expire in 24 hours.\nTEMPORARY PASSWORD: {tempPwd}\n\nYou should change your password as soon as you access your account.";
                Helper.SendEmail(user.Email, title, msgBody);


                // register to database ResetTickets table
                DateTime expireDate = DateTime.Now.AddDays(1); // email expire date

                DB.SaveResetTicket(user.Id, tempPwd, expireDate);

                // go back to LogInControl
                MessageBox.Show("Email sent! Check your inbox.");

                SignWindow signWindow = Helper.GetAncestorOfType <SignWindow>(this);
                if (signWindow != null)
                {
                    signWindow.ShowLogIn();
                }
            }
        }