WpfSample / BorderlessWpf

MainWindow.xaml

<Window x:Class="BorderlessWpf.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="200" Width="200" AllowsTransparency="True" WindowStyle="None" Background="{x:Null}">
    <Grid>
    	<Ellipse Fill="#993399FF" Height="100" Width="100"/>
    </Grid>
</Window>

MainWindow.xaml.cs

using System.Windows;

namespace BorderlessWpf
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            MouseLeftButtonDown += (o, e) => DragMove();
        }
    }
}