Popup can't be made transparent by setting Opacity property

I want to create a Dialog like this pic:

Below is the xaml code of dialog content which is a UserControl and will be put in the Child of Popup:

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             x:Class="AvaloniaApplication10.UserControl1">

  <Grid Background="Gray" Opacity="0.5" >

    <Border Width="200" 
            Height="200" 
            BorderBrush="Red" 
            BorderThickness="2" 
            Background="White">
      <TextBlock Text="Hello World Dialog!" />

    </Border>

  </Grid>

</UserControl>

I’ve subscribed the Bounds property of the MainWindow to make it to cover the full window. But the problem is Opacity=“0.5” has not effect. I also has set the Opacity property of the Popup, but still not working. I also have try to custom the PopupRoot Style, but still can’t make it work.

Is there any way to get this work? Thanks! (The project is Win32)

[EDIT] Just tested WPF and UWP, both can be made transparent by set their child’s transparency properly.

        private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
        {
            Popup po = new Popup();
 
            po.Child = new Border() { Width = 300, Height = 300, 
Background = Brushes.Beige, 
Opacity = 0.5};
            po.StaysOpen = true;
            po.AllowsTransparency = true;
            po.PlacementTarget = sender as FrameworkElement;

            po.IsOpen = true;
        }

[ahopper]

Another way to achieve this is to use a panel covering everything else in your main window and avoid popups altogether.

[maxkatz6]

Shouldn’t be an issue anymore. If it is - ping me here.