How to make WPF Expander Stretch?

Question

The Expander control in WPF does not stretch to fill all the available space. Is there any solutions in XAML for this?

Answer 1

HorizontalAlignment="Stretch"

Answer 2

All you need to do is this:

<Expander>
  <Expander.Header>
    <TextBlock
      Text=”I am header text…”
      Background=”Blue”
      Width=”{Binding
        RelativeSource={RelativeSource
          Mode=FindAncestor,
          AncestorType={x:Type Expander}},
        Path=ActualWidth}”
      />
  </Expander.Header>
  <TextBlock Background=”Red”>
    I am some content…
  </TextBlock>
</Expander>

http://joshsmithonwpf.wordpress.com/2007/02/24/stretching-content-in-an-expander- header/

Answer 3

Non stretchable Expanders is usually the problem of non stretchable parent controls.. Perhaps one of the parent controls has defined a HorizontalAlignment or VerticalAlignment property ?

If you can post some sample code, we can give you a better answer..

HTH

Answer 4

I Agree with HTH - check what sort of a container you're putting the Expander in... the StackPanel will always fold it's children down to the smallest size they can go to.

I'm using Expanders a lot in my project, and if you drop them into a Grid / DockPanel, then the expander will fill all available space (assuming it's Vertical & Horizontal orientations are set to Stretch).

Jonathan's suggestion of Binding the Expander's width to the container's width can get a bit tricky... I tried this technique a few weeks back and found that it can producte undesirable results in some cases, because it can inhibit the functioning of the layout system.

PS: As a general tip (and I'm sure I'm gonna get flamed for writing this), if you're unsure of what sort of layout-container to your controls in, then start off with a Grid. Using the Column & Row definitions allows you to very easily control whether child controls use minimum space ("Auto"), maximum space ("*") or an exact amount of space ("[number]").

Answer 5

The Silverlight Toolkit includes an Accordion control which acts like an expander that always stretches to the available space. I haven't tested it yet, but it might be functional for WPF too, like the Silverlight Chart controls.