How can I extend the style of a DocumentViewer ?

The following style uses the ‘BasedOn’ attribute to extend the default DocumentViewer style.

[XAML]

<Window x:Class='SDKSample.Window1'
        xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation'
        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
  <Window.Resources>
    <Style 
      x:Key='MyDVStyleExtend'
      BasedOn='{StaticResource {x:Type DocumentViewer}}' 
      TargetType='{x:Type DocumentViewer}'>
      <Setter Property='Background'>
        <Setter.Value>
          <LinearGradientBrush StartPoint='0.5,0' EndPoint='0.5,1'>
            <GradientStop Offset='0.0' Color='#CC99CCFF' />
            <GradientStop Offset='1.0' Color='White' />
          </LinearGradientBrush>
        </Setter.Value>
      </Setter>
    </Style>
  </Window.Resources>
  <Grid>
    <DocumentViewer  Style='{StaticResource MyDVStyleExtend}' Name='MyDocumentViewer'/>
  </Grid>
</Window>