C#

Jammer wrote:

Can you clarify what you mean???

<Window x:Class="WpfPartialOpacity.TestWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

    Title="Test Window" Height="300" Width="300"
        AllowsTransparency="True" Background="Transparent" WindowStyle="None">

    <Grid Opacity="0.3" Background="Gray">
    </Grid>

</Window>

namespace WpfPartialOpacity
{
    /// <summary>
    /// Interaction logic for TestWindow.xaml
    /// </summary>
    public partial class TestWindow : Window
    {
        public TestWindow()
        {
            InitializeComponent();
        }

        protected override void OnRender(DrawingContext context)
        {
            base.OnRender(context);

            Rect rect = new Rect(0, 0, Width, Height);

            Pen pen = new Pen(Brushes.Black, 50d);
            context.DrawRectangle(Brushes.Transparent, pen, rect);
        }

    }
}

<Window x:Class="WpfPartialOpacity.TestWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Test Window"
    Height="300" Width="300"
    AllowsTransparency="True"
    Background="Transparent"
    WindowStyle="None">
    <Border BorderThickness="10" BorderBrush="Black">
        <Grid Opacity="0.3" Background="Gray">
                
        </Grid>
    </Border>
</Window>

namespace WpfPartialOpacity
{
    /// 
    /// Interaction logic for TestWindow.xaml
    /// 
    public partial class TestWindow : Window
    {
        public TestWindow()
        {
            InitializeComponent();
        }
    }
}

<Grid x:name="MainVisualHost" opacity="0.3" background="Gray">
                
</grid>

MainVisualHost.Children.Add(yourcontrolobject)