How can I get the actual grid row height of a grid with RowDefinition Height *

     <Grid x:Name="SidebarGrid" LayoutUpdated="gridlayoutupdated">
            <Grid.RowDefinitions>
                <RowDefinition Height="250" />
                <RowDefinition Height="*"/>
                <RowDefinition Height="*" />
            </Grid.RowDefinitions>

The Row sizes to content, but after the content is set, I would like to get the height.