private void LogIn_Click(object sender, RoutedEventArgs e)
        {
            AuthWindow auth = new AuthWindow();

            auth.Show();
            this.Hide();
        }
        private void SignUp_Click(object sender, RoutedEventArgs e)
        {
            string log      = login.Text.Trim();
            string pass     = password.Password.Trim();
            string pass_rep = password_repeat.Password.Trim();
            string mail     = email.Text.Trim().ToLower();

            bool login_check    = false;
            bool pass_check     = false;
            bool pass_rep_check = false;
            bool email_check    = false;

            if (log.Length < 6)
            {
                login.ToolTip    = "Length of login is less than 6 symbols";
                login.Background = Brushes.LightGoldenrodYellow;
                login_check      = false;
            }
            else
            {
                login.ToolTip    = null;
                login.Background = Brushes.Transparent;
                login_check      = true;
            }

            if (pass != pass_rep)
            {
                password.ToolTip           = "Passwords do not match";
                password_repeat.ToolTip    = "Passwords do not match";
                password.Background        = Brushes.LightGoldenrodYellow;
                password_repeat.Background = Brushes.LightGoldenrodYellow;
                pass_check     = false;
                pass_rep_check = false;
            }
            else
            {
                password.ToolTip           = null;
                password.Background        = Brushes.Transparent;
                password_repeat.ToolTip    = null;
                password_repeat.Background = Brushes.Transparent;
                pass_check     = true;
                pass_rep_check = true;
            }

            if (pass.Length < 6)
            {
                password.ToolTip    = "Length of password is less than 6 symbols";
                password.Background = Brushes.LightGoldenrodYellow;
                pass_check          = false;
            }
            else
            {
                password.ToolTip    = null;
                password.Background = Brushes.Transparent;
                pass_check          = true;
            }

            if (mail.Length < 6 || !mail.Contains("@") || !mail.Contains("."))
            {
                email.ToolTip    = "Wrong email input (Must contain '@','.'; Length should be at least 6 symbols;)";
                email.Background = Brushes.LightGoldenrodYellow;
                email_check      = false;
            }
            else
            {
                email.ToolTip    = null;
                email.Background = Brushes.Transparent;
                email_check      = true;
            }

            if (login_check && pass_check && pass_rep_check && email_check)
            {
                login.ToolTip              = null;
                login.Background           = Brushes.Transparent;
                password.ToolTip           = null;
                password.Background        = Brushes.Transparent;
                password_repeat.ToolTip    = null;
                password_repeat.Background = Brushes.Transparent;
                email.ToolTip              = null;
                email.Background           = Brushes.Transparent;

                db.Users.Add(new User(log, pass, mail));
                db.SaveChanges();

                AuthWindow auth = new AuthWindow();
                auth.Show();
                this.Hide();
            }
        }