How do I stretch the contents of a HeaderedContentControl? - wpf

Question

I have a HeaderedContentControl that contains a TreeView.
<HeaderedContentControl Header="Steps" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
<TreeView Name="WizardSteps" ItemsSource="{Binding WizardSteps}" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
<!-- Hierarchical data templates here -->
</TreeView>
</HeaderedContentControl>
Although the HeaderedContentControl stretches to fill the area inside its parent grid, my TreeView control only occupies a small portion of the space available.
How do I get my TreeView to expand to fill the content area of my HeaderedContentControl?

Answer 1

The default control template for HeaderedContentControl is something like this:
<ControlTemplate TargetType="{x:Type HeaderedContentControl}">
<StackPanel>
<ContentPresenter ContentSource="Header" />
<ContentPresenter />
</StackPanel>
</ControlTemplate>
The StackPanel lets each child have its own desired height, so the TreeView won't stretch. You could replace it with a template that uses a DockPanel:
<HeaderedContentControl Header="Steps" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" VerticalContentAlignment="Stretch" >
<HeaderedContentControl.Template>
<ControlTemplate TargetType="HeaderedContentControl">
<DockPanel>
<ContentPresenter DockPanel.Dock="Top" ContentSource="Header" />
<ContentPresenter />
</DockPanel>
</ControlTemplate>
</HeaderedContentControl.Template>
If you want to make it more reusable, set the template in a Style and use VerticalContentAlignment:
<Style TargetType="HeaderedContentControl">
<Setter Property="VerticalContentAlignment" Value="Stretch"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="HeaderedContentControl">
<DockPanel>
<ContentPresenter DockPanel.Dock="Top" ContentSource="Header" />
<ContentPresenter VerticalAlignment="{TemplateBinding VerticalContentAlignment}" />
</DockPanel>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
That way, all your HeaderedContentControls will have their content fill by default, and you can override that by setting VerticalContentAlignment on an individual control.
Alternately, you could use a DockPanel directly instead of a HeaderedContentControl.