WPF DocumentViewer loses custom style after internal link use - wpf

Question

Hi want to build a small application, that allows to navigate through filesystem and displays several documents. One type of document i want to show, is xps. DocumentViewer is doing well. In combination with a Frame the viewer can handle internal links (included in the xps documents.). For my Application i build a custom toolbar (zoom, page, fitsize ...), to have a one toolbar for every kind of document. So i needed to remove the toolbar of the documentViewer. Below is the code.
<Style x:Key="{x:Type DocumentViewer}"
TargetType="{x:Type DocumentViewer}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type DocumentViewer}">
<Border BorderThickness="{TemplateBinding BorderThickness}"
BorderBrush="{TemplateBinding BorderBrush}"
Focusable="False">
<ScrollViewer
CanContentScroll="true"
HorizontalScrollBarVisibility="Auto"
x:Name="PART_ContentHost"
IsTabStop="true">
</ScrollViewer>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
That works fine, but after activating a link in the xps, the DocumentViewer Toolbar appears again. How to avoid that?

Answer 1

The problem is that the navigation service creates a new standard DocumentViewer after clicking on a link for the first time. This happens even when you use a component derived from DocumentViewer in your XAML.
You can work around this issue by manually resetting the style in your navigation container's LayoutUpdated event
XAML
<Frame LayoutUpdated="OnFrameLayoutUpdated">
<Frame.Content>
<DocumentViewer ... />
</Frame.Content>
</Frame>
Code behind
private void OnFrameLayoutUpdated(object sender, EventArgs e)
{
var viewer = GetFirstChildByType<DocumentViewer>(this);
if (viewer == null) return;
viewer.Style = (Style) FindResource("DocumentViewerStyle");
}
private T GetFirstChildByType<T>(DependencyObject prop) where T : DependencyObject
{
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(prop); i++)
{
DependencyObject child = VisualTreeHelper.GetChild((prop), i) as DependencyObject;
if (child == null)
continue;
T castedProp = child as T;
if (castedProp != null)
return castedProp;
castedProp = GetFirstChildByType<T>(child);
if (castedProp != null)
return castedProp;
}
return null;
}