Dark theme of app - windows

Question

I writing application for Windows phone.
I want to set dark theme of app.
I set it on this window, but when I deploy this app on device, my theme is light.
Theme
Code of my xaml:
<Page
x:Class="Murakami.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:Murakami"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<Button x:Name="button" Content="" HorizontalAlignment="Left" Margin="10,10,0,0" VerticalAlignment="Top" Width="48" Height="46">
<Button.Background>
<ImageBrush Stretch="Fill" ImageSource="Images/menu.png"/>
</Button.Background>
</Button>
<Button x:Name="button1" Content="" HorizontalAlignment="Left" Margin="302,10,0,0" VerticalAlignment="Top" Width="48" Height="46" >
<Button.Background>
<ImageBrush Stretch="Fill" ImageSource="Images/cart.png"/>
</Button.Background>
</Button>
<Button x:Name="button2" Content="" HorizontalAlignment="Left" Margin="126,5,0,0" VerticalAlignment="Top" Height="63" Width="115">
<Button.Background>
<ImageBrush Stretch="Fill" ImageSource="Images/logo_murakami.png"/>
</Button.Background>
</Button>
</Grid>
How I can fix this?