How to set the scrollviewer size to the parent's grid size in wpf

Question

I have a popup control in a grid and I want it to resize to the parent grid size. As you can see the parent grid area is in Green color and the popup is in LightCyan color. The area in the LightCyan should cover the whole green area. And I think I have to set the Scrollviewer width and height to the parent's width and height but that didn't work. Please reply. Thanks

I am adding different stuff in the LinePopGrid using code.

<Grid Background="Green">
<Popup x:Name="LinePopUp" IsOpen="True" Placement="Relative" >
        <ScrollViewer  CanContentScroll="True" VerticalScrollBarVisibility="Auto">
            <Grid Background="LightCyan" x:Name="LinePopUpGrid" />
        </ScrollViewer>
    </Popup>
</Grid>

Answer 1

You need to bind PopUp width and height to Grid's ActualWidth and ActualHeight respectively -

<Grid Background="Green">
        <Popup x:Name="LinePopUp" IsOpen="True" Placement="Relative"
               Width="{Binding ActualWidth,RelativeSource={RelativeSource 
                               Mode=FindAncestor, AncestorType=Grid}}"                   
               Height="{Binding ActualHeight,RelativeSource={RelativeSource
                                Mode=FindAncestor, AncestorType=Grid}}">
            <ScrollViewer CanContentScroll="True"
                          VerticalScrollBarVisibility="Auto">
                <Grid Background="LightCyan" x:Name="LinePopUpGrid" />
            </ScrollViewer>
        </Popup>
 </Grid>