WPF C#

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="BookApp" Height="300" Width="300">
    
      Go
    


//File:Window.xaml.cs
using System;
using System.Collections.Generic;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
namespace BookApp
{
    public partial class Window1 : System.Windows.Window
    {
        public Window1()
        {
            InitializeComponent();
            Book x = new Book();
            x.author = "A";
            x.title = "title";
            x.price = (decimal)9.99;
            Application.Current.Properties["Book"] = x;
        }
        private void MyClickEvent(object sender, RoutedEventArgs e)
        {
            Book y = (Book)Application.Current.Properties["Book"];
            MessageBox.Show(y.title, y.author, MessageBoxButton.OK,MessageBoxImage.Hand);
        }
    }
    public class Book
    {
        public decimal price;
        public string title;
        public string author;
    }
}