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.
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 Directive.
<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>
