How to: Replace the Default Content Host for a RichTextBox
This example shows how to use Windows Presentation Foundation (WPF) styles to replace the default content host for a RichTextBox.
The content host is the element that renders the contents of the RichTextBox. The default control template for a RichTextBox specifies a ScrollViewer as the content host.
In cases where the scrolling features provided by a ScrollViewer are unwanted or unneeded, a lighter-weight AdornerDecorator element may be specified as the content host for a RichTextBox. ScrollViewer and AdornerDecorator are the only supported elements for the content host.
For a working sample that demonstrates this example, see Replace the Default Content Host for a RichTextBox Sample.
Example
The ControlTemplate for a RichTextBox must contain exactly one element that is tagged as the content host element. To tag an element as the content host, assign it the special name PART_ContentHost. The content host element must be either a ScrollViewer or an AdornerDecorator. The content host element may not host any child elements.
The following Extensible Application Markup Language (XAML) example defines a style that overrides the default control template for a RichTextBox. This style is compatible with elements that descend from TextBoxBase. In the example, an AdornerDecorator is specified as the content host.
<Window.Resources>
<Style x:Key="TextBoxNoScrollViewer" TargetType="{x:Type TextBoxBase}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TextBoxBase}">
<Border
CornerRadius="2"
Background="{TemplateBinding Background}"
BorderThickness="{TemplateBinding BorderThickness}"
BorderBrush="{TemplateBinding BorderBrush}"
>
<!--
The control template for a TextBox or RichTextBox must
include an element tagged as the content host. An element is
tagged as the content host element when it has the special name
PART_ContentHost. The content host element must be a ScrollViewer,
or an element that derives from Decorator.
-->
<AdornerDecorator
x:Name="PART_ContentHost"
Focusable="False"
/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Window.Resources>
The following XAML example defines a RichTextBox that makes use of the previously declared style by using the Style attribute coupled with a static resource reference to the style's x:Key Attribute.
<RichTextBox
Grid.Column="0"
VerticalScrollBarVisibility="Auto"
HorizontalScrollBarVisibility="Auto"
Style="{StaticResource TextBoxNoScrollViewer}"
>
<FlowDocument>
<Paragraph>
RichTextBox styled not to use a ScrollViewer as the content host.
</Paragraph>
</FlowDocument>
</RichTextBox>