WPF Combobox switch up and down then show the big picture in the right part

<ComboBox x:Name="cbx"
          Grid.Row="0"
          Grid.Column="0"
          SelectedIndex="0"
          ItemsSource="{StaticResource booksData}"                  
          FontSize="20" Foreground="Red" 
          VerticalAlignment="Stretch" 
          HorizontalAlignment="Stretch" 
          BorderBrush="Blue" 
          BorderThickness="3"
          VirtualizingPanel.IsContainerVirtualizable="True"
          VirtualizingPanel.IsVirtualizing="True"
          VirtualizingPanel.CacheLength="1"
          VirtualizingPanel.CacheLengthUnit="Item"
          VirtualizingPanel.VirtualizationMode="Recycling"
          IsDropDownOpen="True"
    >
    <ComboBox.ItemTemplate>
        <DataTemplate>
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition/>
                    <RowDefinition Height="10*"/>
                    <RowDefinition/>
                </Grid.RowDefinitions>
                <TextBlock Text="{Binding Name}" Grid.Row="0"/>
                <TextBlock Text="{Binding ImgUrl}" Grid.Row="2"/>
                <Image Source="{Binding ImgUrl}" Width="200" Height="500" 
                       Grid.Row="1"/>
            </Grid>
        </DataTemplate>
    </ComboBox.ItemTemplate>
</ComboBox>
<Image Source="{Binding SelectedItem.ImgUrl,ElementName=cbx}" Grid.Column="1" Grid.Row="0" Grid.RowSpan="2" Stretch="Uniform"
       x:Name="img" RenderOptions.BitmapScalingMode="LowQuality"/>