<Window x:Class="WpfApp1.Window1" 
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
xmlns:local="clr-namespace:WpfApp1" 
mc:Ignorable="d" 

 Title="MainWindow" Height="700" Width="450" AllowsTransparency="True" Background="Transparent" WindowStyle="None" ResizeMode="CanResizeWithGrip" Topmost="True">
    <Grid Margin="-23,-31,0,0">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="0*"/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Border Width="Auto" Height="Auto" Name="windowFrame" 

BorderBrush="#395984" 
Background="#002342" 
Opacity="0.5" 

BorderThickness="10" 
CornerRadius="10,10,10,10" Margin="28,37,10,10" Grid.ColumnSpan="2" >
        </Border>




        <Button x:Name="closeButton" Click="closeButton_Click" Content="Close" Margin="156,543,122,135" Grid.ColumnSpan="2" />

        <Border x:Name="border1" BorderBrush="Black" BorderThickness="1" HorizontalAlignment="Left" Height="10" Background="#fff" VerticalAlignment="Top" Width="338" Margin="56,643,0,0" Grid.ColumnSpan="2"/>
        <MediaElement Grid.ColumnSpan="2" Source="" HorizontalAlignment="Left" Height="151" Margin="90,106,0,0" VerticalAlignment="Top" Width="304"/>


    </Grid>
</Window>

public double screenHeight = SystemParameters.FullPrimaryScreenHeight;
        public double screenWidth = SystemParameters.FullPrimaryScreenWidth;
        this.Top = (screenHeight - transparentWindows.Height) / 0x00000002;
        this.Left = (screenWidth - transparentWindows.Width) / 0x00000002;