WPF - Scrolling Listbox in an Expander

Question

I have an Expander that I want to have a ListBox in. When the I open the expander the ListBox just expands off the screen (rather than expanding to fill what is available and then scrolling)

Here is my XAML:

<DockPanel Margin="266.25,0,455,12" Name="dockPanel1">
    <StackPanel>
        <Expander Header="expander1" Name="expander1" Width="150" HorizontalAlignment="Left">
            <Grid>
                <Label>Testing</Label>
                <ScrollViewer>
                    <ListBox Name="lstBox"  FontSize="14" SelectionChanged="lstBox_SelectionChanged" />
                </ScrollViewer>
            </Grid>
        </Expander>
        <Expander Header="expander2" Name="expander2" Width="150" HorizontalAlignment="Left">
            <Grid >

            </Grid>
        </Expander>
    </StackPanel>
</DockPanel>

When Expander1 is opened then it just expands to the size of the ListBox (off the screen). If I put a size on the grid (Height="275"), then it does not resize with the window.

I want it to stretch to the size of the window, but no more. Is there a way to do that?

Answer 1

You need to set the Height property of ScrollViewer otherwise it will be the same size as it's child. Here is some updated XAML:

<DockPanel>
 <StackPanel>
  <Expander Header="expander1" Width="150" HorizontalAlignment="Left">
   <StackPanel>
    <Label>Testing</Label>
    <ScrollViewer Height="75">
     <ListBox>

     </ListBox>
    </ScrollViewer>
   </StackPanel>
  </Expander>
  <Expander Header="expander2">
  </Expander>
 </StackPanel>
</DockPanel>