// -- CRUD -- //

        // Add new user
        private void addButton_Click(object sender, RoutedEventArgs e)
        {
            using (var db = new SimpleScadaContext())
            {
                db.Users.Add(new Users()
                {
                    User = usernameTxt.Text, Password = passwordTxt.Text, Level = Int32.Parse(levelTxt.Text)
                });
                db.SaveChanges();

                showViewList();
            };
        }
        // Delete choosen user
        private void deleteButton_Click(object sender, RoutedEventArgs e)
        {
            var selectedStockObject = userList.SelectedItem as Users;

            using (var db = new SimpleScadaContext())
            {
                var newUser = db.Users.First(p => p.Id == selectedStockObject.Id);
                db.Users.Remove(newUser);
                db.SaveChanges();

                showViewList();
            };
        }
        // Edit choosen user
        private void editButton_Click(object sender, RoutedEventArgs e)
        {
            var selectedStockObject = userList.SelectedItem as Users;

            using (var db = new SimpleScadaContext())
            {
                db.Users.First(p => p.Id == selectedStockObject.Id).User     = usernameTxt.Text;
                db.Users.First(p => p.Id == selectedStockObject.Id).Password = passwordTxt.Text;
                db.Users.First(p => p.Id == selectedStockObject.Id).Level    = Int32.Parse(levelTxt.Text);
                db.SaveChanges();

                showViewList();
            };
        }