Code

<diag:DiagramView>
    <diag:DiagramView.Style>
        <Style TargetType="{x:Type ScrollViewer}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type ScrollViewer}">
                        <Grid>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition />
                                <ColumnDefinition Width="Auto" />
                            </Grid.ColumnDefinitions>
                            <Grid.RowDefinitions>
                                <RowDefinition />
                                <RowDefinition Height="Auto" />
                            </Grid.RowDefinitions>
                            <Border Grid.Column="0" BorderThickness="0,1,1,1">
                                <ScrollContentPresenter
                                    HorizontalAlignment="Left"
                                    VerticalAlignment="Top" />
                            </Border>
                            <ScrollBar x:Name="PART_VerticalScrollBar"
                                 Grid.Column="1"
                                 Value="{TemplateBinding VerticalOffset}"
                                 Maximum="{TemplateBinding ScrollableHeight}"
                                 ViewportSize="{TemplateBinding ViewportHeight}"
                                 Visibility="{TemplateBinding ComputedVerticalScrollBarVisibility}"/>
                            <ScrollBar x:Name="PART_HorizontalScrollBar"
                                 Orientation="Horizontal"
                                 Grid.Row="1"
                                 Value="{TemplateBinding HorizontalOffset}"
                                 Maximum="{TemplateBinding ScrollableWidth}"
                                 ViewportSize="{TemplateBinding ViewportWidth}"
                                 Visibility="{TemplateBinding ComputedHorizontalScrollBarVisibility}"/>
                        </Grid>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </diag:DiagramView.Style>
    <diag:Diagram Bounds="0, 0, 100,100"  />
</diag:DiagramView>