WPF display image and can scroll both in horizontally and vertically in the ScrollViewer

//xaml
<Window x:Class="WpfApp44.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:WpfApp44"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <DockPanel>
        <Button DockPanel.Dock="Top" FontSize="20" Margin="4" Padding="4" Click="Button_Click" Width="200" Height="50" HorizontalAlignment="Left">
            <StackPanel Orientation="Horizontal">
                <Image Source="pack://application:,,,/Images/cl4.jpg" />
                <TextBlock Text="Open Image File..." Margin="20,0,0,0"
                           VerticalAlignment="Center"/>
            </StackPanel>
        </Button>
        <ScrollViewer BorderBrush="Black" Margin="4" BorderThickness="1" HorizontalScrollBarVisibility="Auto"
                      VerticalScrollBarVisibility="Auto">
            <Image x:Name="_img" Stretch="None"/>
        </ScrollViewer>
    </DockPanel>
</Window>


//cs
using Microsoft.Win32;
using System;
using System.Collections.Generic;
using System.ComponentModel.Design.Serialization;
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 WpfApp44
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            var dlg = new OpenFileDialog();
            dlg.Filter = "Images|*.jpg;*.gif;*.bmp;*.png";
            if(dlg.ShowDialog()==true)
            {
                try
                {
                    var bmp = new BitmapImage(new Uri(dlg.FileName, UriKind.Absolute));
                    _img.Source = bmp;
                }
                catch(Exception ex)
                {
                    MessageBox.Show("Error loading image: " + ex.Message);
                }
            }
        }
    }
}