Scroll Appearing Problem MVVM - WPF

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WPF

MVVM

Canvas

scrolling

Hi Everyone,
I tried to implement drag-drop application with mvvm in WPF. Everything is ok, but when the out of range, scroll is not appearing. For Example, DropArea is 600x800. If item location is (300,850), the vertical scrollbar is expected to be visible, and the horizontal scrollbar is expected to be invisible. How can I provided that?

Thanks in advance.

<ControlTemplate x:Key="CanvasTemplate">
    <Grid>
        <ScrollViewer x:Name="ScrollViewer" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto" >
            <Border removed="{Binding Path=Background,Converter={StaticResource ColorBrushConverter}}">
                <ItemsPresenter x:Name="ItemsPresenter"/>
            </Border>
        </ScrollViewer>
    </Grid>
</ControlTemplate>


<ItemsControl x:Name="ic" DataContext="{Binding Path=CanvasViewModel}" ItemsSource="{Binding Path=Items}" Width="Auto" Height="Auto" VerticalAlignment="Stretch"
            HorizontalAlignment="Stretch" ItemTemplateSelector="{StaticResource ItemDatatemplateSelector}" Template="{StaticResource CanvasTemplate}"
            >
    <ItemsControl.ItemsPanel>
    <ItemsPanelTemplate>
        <Canvas IsItemsHost="True" DataContext="{Binding ElementName=ic, Path=DataContext}" Width="Auto" Height="Auto" VerticalAlignment="Stretch" HorizontalAlignment="Stretch"
                                Background="Transparent" AllowDrop="True"
                                    >
                </Canvas>
    </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>

        <ItemsControl.ItemContainerStyle>
        <Style>
            <Setter Property="Canvas.Left" Value="{Binding Path=Left}"/>
            <Setter Property="Canvas.Top" Value="{Binding Path=Top}"/>
        </Style>
    </ItemsControl.ItemContainerStyle>
</ItemsControl>