WPF draw random ellipse and locate via coordinate

//xaml
<Window x:Class="WpfApp181.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp181"
        mc:Ignorable="d" WindowState="Maximized"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition/>
            <RowDefinition Height="200"/>
        </Grid.RowDefinitions>
        <Canvas x:Name="cvs" Grid.Row="0" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"/>
        <DataGrid x:Name="dg" Grid.Row="1" SelectionChanged="dg_SelectionChanged" 
                  SelectionMode="Single" />
    </Grid>
</Window>


//cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
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.Navigation;
using System.Windows.Shapes;

namespace WpfApp181
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        Ellipse markedElp { get; set; }
        public MainWindow()
        {
            InitializeComponent();
            markedElp = new Ellipse();
            markedElp.Width = 30;
            markedElp.Height = 30;
            markedElp.Stroke = new SolidColorBrush(Colors.Red);
            markedElp.Fill = new SolidColorBrush(Colors.Red);
            this.Loaded += MainWindow_Loaded; 
        }

        private void MainWindow_Loaded(object sender, RoutedEventArgs e)
        { 
            InitElps();
        }

        private void InitElps()
        {
            List<Book> booksList = new List<Book>();
            int width = (int)cvs.ActualWidth - 50;
            int height = (int)cvs.ActualHeight - 50;
            Random rnd = new Random();
            for (int i = 0; i < 1000; i++)
            {
                int x=rnd.Next(0, width);
                int y=rnd.Next(0, height);
                Book bk = new Book();
                bk.Id = i + 1;
                bk.PtX = x;
                bk.PtY = y;
                booksList.Add( bk );
                Ellipse elp = new Ellipse();
                elp.Stroke = new SolidColorBrush(Colors.Cyan);
                elp.StrokeThickness = 3;
                elp.Width = 20;
                elp.Height = 20;
                elp.Fill = new SolidColorBrush(Colors.Blue);
                Canvas.SetLeft(elp, x);
                Canvas.SetTop(elp, y);
                cvs.Children.Add ( elp );
            }
            dg.ItemsSource= booksList;
        }

        private void dg_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            if(e.AddedItems!=null && e.AddedItems.Count>0)
            {
                var selectedBk = e.AddedItems[0] as Book;
                if(selectedBk != null)
                {
                    if(cvs.Children.Contains(markedElp))
                    {
                        cvs.Children.Remove(markedElp);
                    }
                    Canvas.SetLeft(markedElp,selectedBk.PtX);
                    Canvas.SetTop(markedElp,selectedBk.PtY);
                    cvs.Children.Add(markedElp);
                }
            }
        }
    }


    public class Book
    {
        public int Id { get; set; }
        public int PtX { get; set; }
        public int PtY { get; set; }
    }
}