WPF Datagrid AutoScroll via behavior

public class DataGridAutoScrollBehavior:Behavior<DataGrid>
{
    protected override void OnAttached()
    {
        base.OnAttached();
        AssociatedObject.SelectionChanged += AssociatedObject_SelectionChanged;
    }

    private void AssociatedObject_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        var dg= sender as DataGrid;
        if (dg!=null && dg.SelectedItem!=null)
        {
            dg.ScrollIntoView(dg.SelectedItem);
        }
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();
        AssociatedObject.SelectionChanged -= AssociatedObject_SelectionChanged;
    }
}





<Window x:Class="WpfApp47.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:behavior="http://schemas.microsoft.com/xaml/behaviors"
        WindowState="Maximized"
        xmlns:local="clr-namespace:WpfApp47"
        mc:Ignorable="d"
        Title="{Binding SelectedBk.ISBN}" Height="450" Width="800">
    <Window.DataContext>
        <local:BookVM/>
    </Window.DataContext>
    <Grid>
        <DataGrid ItemsSource="{Binding BooksCollection,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
                  SelectedItem="{Binding SelectedBk,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
                  SelectedIndex="{Binding SelectedIdx,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
                  AutoGenerateColumns="False"
                  CanUserAddRows="False"
                  VirtualizingPanel.IsContainerVirtualizable="True"
                  VirtualizingPanel.IsVirtualizing="True"
                  VirtualizingPanel.CacheLength="1"
                  VirtualizingPanel.CacheLengthUnit="Item">
            <behavior:Interaction.Behaviors>
                <local:DataGridAutoScrollBehavior/>
            </behavior:Interaction.Behaviors>             
            <DataGrid.Columns>               
                <DataGridTemplateColumn Header="Image">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <local:ImgTbk UCImgSource="{Binding DataContext.ImgSource,
                                RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type DataGridRow}}}"
                                          UCStr="{Binding DataContext.ISBN,
                                RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type DataGridRow}}}"/>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</Window>