How to draw horizontal line in my end of list in WPF?

Question

I want a blue line stretch end listitem but only a few come.

I gave

HorizontalAlignment = "Stretch"

but it doesn't work.

Full list code here

 <Grid>
        <ListBox Name="MyListBoxAddData" Margin="20" BorderThickness="0">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel>
                        <Label Content="{Binding Id}"/>
                        <Label Content="{Binding  Path=Questions,Mode=TwoWay}"/>
                        <RadioButton Content="{Binding  Path=Option1,Mode=TwoWay}" Margin="10 5"/>
                        <RadioButton Content="{Binding Path=Option2,Mode=TwoWay}" Margin="10 5"/>
                        <RadioButton Content="{Binding Path=Option3,Mode=TwoWay}" Margin="10 5"/>
                        <RadioButton Content="{Binding Path=Option4,Mode=TwoWay}" Margin="10 5"/>
                        <TextBlock Text="{Binding Answer}" />
                        <Separator HorizontalContentAlignment="Stretch"/>
                        <Rectangle HorizontalAlignment="Stretch"  Fill="Blue" Height="4" />
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </Grid>

O/P

I want a full line. Thank you in Advance

Answer 1

Set the ListBox's HorizontalContentAlignment property to Stretch:

<ListBox Name="MyListBoxAddData" Margin="20" BorderThickness="0"
         HorizontalContentAlignment="Stretch">
    ...
</ListBox>