如何使ComboBox填充UWP中包含的网格线的所有空间

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="Auto"/>
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="Auto"/>
        <ColumnDefinition Width="Auto"/>
    </Grid.ColumnDefinitions>

    <ComboBox Grid.Row="0" Grid.Column="0" 
               VerticalAlignment="Stretch" 
               HorizontalAlignment="Stretch" 
               Margin="0"
               <!-- 其他属性设置 -->
               />

    <!-- 其他控件或内容 -->
</Grid>