请问wpf里，我想设置主窗口透明度与控件透明度不一样，该如何设置？

如题，比如主窗口的透明度为0.2，我想设置里面grid里嵌套的grid里的一个label或者button的透明度为0.8，该如何设置?

 <Window x:Class="TopUI.TopCover"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525" WindowState="Maximized"
        WindowStyle="None" Opacity="0.01" AllowsTransparency="True" Cursor="Hand">
    <Grid MouseMove="Grid_MouseMove" Background="Black" MouseLeftButtonDown="Grid_MouseLeftButtonDown" MouseWheel="Grid_MouseWheel">
        <Grid.RowDefinitions>
            <RowDefinition Height="60"></RowDefinition>
            <RowDefinition/>
            <RowDefinition Height="60"/>
        </Grid.RowDefinitions>
        <Grid Grid.Row="0" HorizontalAlignment="Center" VerticalAlignment="Center">
            <Label Name="labLocationInfo" Content="121212" Width="100" Opacity="0.9" Foreground="Yellow"/>
        </Grid>
    </Grid>
</Window>

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525" WindowState="Maximized"
WindowStyle="None" Opacity="0.01" AllowsTransparency="True" Cursor="Hand">

不要用设置Opacity="0.01"，会影响子控件，设置alpha值， AllowsTransparency="True" Background="#11ffffff"