private void loginBtn_Click(object sender, RoutedEventArgs e)
 {
     if (usernameTxt.Text != null && passPbx.Password != null)
     {
         string username = usernameTxt.Text;
         //string password = passTxt.Text;
         string password = passPbx.Password;
         context = new DynamoDBContext(client);
         //Table UserTable = Table.LoadTable(client, "Users");
         User getUser = context.Load <User>(username);
         if (username == "ADMIN" && password == "password")
         {
             AdminWindow adw = new AdminWindow();
             adw.Show();
         }
         else if (getUser != null && getUser.Password == password)
         {
             errorMsgLbl.Content = "";
             UserBookshelfWindow usbsw = new UserBookshelfWindow(getUser);
             usbsw.Show();
         }
         else
         {
             errorMsgLbl.Content = "**Wrong username/password.";
         }
     }
     else
     {
         errorMsgLbl.Content = "**Please put username/password";
     }
 }
        protected override void OnClosing(System.ComponentModel.CancelEventArgs e)
        {
            User retrieved          = context.Load <User>(user.Username);
            UserBookshelfWindow ubs = new UserBookshelfWindow(retrieved);

            ubs.Show();
        }
        protected override void OnClosing(System.ComponentModel.CancelEventArgs e)
        {
            currentpage = viewer.CurrentPageNumber;
            context     = new DynamoDBContext(client);
            User retrieved = context.Load <User>(user.Username);

            retrieved.Books.Where(b => b.ISBN == book.ISBN)
            .Select(b => b)
            .First().CurrentPage = currentpage;
            context.Save <User>(retrieved);
            UserBookshelfWindow ubsw = new UserBookshelfWindow(retrieved);

            ubsw.Show();
            base.OnClosing(e);
        }