How can I hide the top bar in wpf main window ?

I marked with red ellipse what part I mean that I want to hide when running the application.

I tried to add to the MainWindow.xmal this line :

 WindowStyle="None"  

But it didn't hide it.

<Window x:Class="Wpf_Download_Files.MainWindow"  
        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:Wpf_Download_Files"  
        mc:Ignorable="d"  
        WindowStyle="None"  
        Title="MainWindow" Height="450" Width="800">