<Page
    x:Class="backgroundblurtest.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:backgroundblurtest"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="Transparent">
        <RelativePanel Grid.Column="0" Grid.ColumnSpan="2" MinWidth="40" x:Name="MainGrid" SizeChanged="Page_SizeChanged" Loaded="Page_Loaded"/>
        <RelativePanel Grid.Column="0" Width="{Binding ElementName=MainGrid,Path=Width}" Background="#28000000"/>
        <Grid>
            <!--Having content here, for example textblock and so on-->
            <TextBlock HorizontalAlignment="Left" Text="TextBlock" VerticalAlignment="Top"/>
        </Grid>
    </Grid>
</Page>