How can this layout work

Hi all,

I'm trying to test the following on WP and the entry won't take up the rest of the page. I'm trying to use PushModalAsync with this.

      <ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="TestPage"
             Title="Add exercise">
     <Grid HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand">

        <!--<Label Grid.Row="0" Text="bad" Font="Bold,50" HorizontalOptions="FillAndExpand"/>-->
        <!--<Label Grid.Row="0" Text="good label because its long enough" Font="Bold,50" HorizontalOptions="FillAndExpand"/>-->
        <ScrollView Grid.Row="1" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand">
            <Grid Padding="10" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="110" />
                    <ColumnDefinition Width="*" />
                    <ColumnDefinition Width="Auto" />
                </Grid.ColumnDefinitions>

                <Label Grid.Row="2" Grid.Column="0" Text="Name" VerticalOptions="Center" />
                <Entry Grid.Row="2" Grid.Column="1" Grid.ColumnSpan="2" Text="{Binding Name}"
                       HorizontalOptions="FillAndExpand" />

            </Grid>
        </ScrollView>
    </Grid>

    <ContentPage.ToolbarItems>
        <ToolbarItem Name="ok" Icon="check.png" Command="{Binding SaveCommand}"></ToolbarItem>
    </ContentPage.ToolbarItems>

    </ContentPage>

The entry refuses to take up the whole page unless the "good" label is uncommented above and the text is long enough to fill the screen

thanks

cliff