How to stretch group header content to fill up the entire row?

[Wenrong]

My group header has a custom background, some text that need to align to the left, and some to the right. But now they are all crammed to the left of the header row. How can I make it stretch?

My header template:

<DataTemplate x:Key="alarmGridGroupTemplate">
    <Grid Background="{Binding Group.Key, Converter={StaticResource priorityToBrushConverter}}" Height="26" VerticalAlignment="Center">
        <Grid.Resources>
            <Style TargetType="{x:Type TextBlock}">
                <Setter Property="FontSize" Value="14" />
                <Setter Property="Foreground" Value="White" />
                <Setter Property="VerticalAlignment" Value="Center" />
            </Style>
        </Grid.Resources>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="Auto" />
            <ColumnDefinition Width="Auto" />
        </Grid.ColumnDefinitions>

        <TextBlock Text="{Binding Path=Group.Key, Converter={StaticResource priorityToDescriptionConverter}}" Margin="3.5,0" />
        <TextBlock Grid.Column="1" Text="Count:" />
        <TextBlock Grid.Column="2" Text="{Binding Group.ItemCount}" TextAlignment="Right" Margin="5,0,11,0" />
    </Grid>
</DataTemplate>

[Maya]

Hi Wenrong,

You need to edit the template of GridViewGroupRow and change the elements you want as illustrated in our online documentation. 

Kind regards,
Maya
the Telerik team