How to make WPF Expander Stretch?

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

From stackoverflow

• HorizontalAlignment="Stretch"
  

  Ngm : This is not working

• 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/

  Ngm : How do I do this in code? I realized that I have to account for some space for a button

  Jonathan Parker : Sorry I don't know how to do it in code.

  Josh G : TextBlock bx = new TextBlock(); bx.Text = "I am header text..."; Binding wdBind = new Binding("ActualWidth"); wdBind.RelativeSource = new RelativeSource(RelativeSourceMode.FindAncestor, typeof(Expander), 1); bx.SetBinding(TextBlock.TextProperty, wdBind);

  Josh G : bx.Background = Colors.Blue; Expander ex = new Expander(); ex.Header = bx;

  Josh G : TextBlock contBx = new TextBlock(); contBx.Background = Colors.Red; contBx.Text = "I am some content..."; ex.Content = contBx;

  Josh G : ... This code is exactly equivalent to the XAML above.

  Jonathan Parker : Josh, you can always put this code in your own answer. That way it's more visible and can be voted on and marked as the answer.

• 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

• 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]").

  Josh G : Grid is definitely the most versatile and easy to use container. I've heard that it performs much worse than most containers also.

  Bryan Anderson : @Mark, you mean you agree with Arcturus. HTH means Hope That Helps and is a common closing around here.

• 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.