WPF 테두리 없는 투명 창 크기 조절

<Window x:Class="WpfResizeWindow.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300" WindowStyle="None" AllowsTransparency="True">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="4"/>
            <RowDefinition/>
            <RowDefinition Height="4"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="4"/>
            <ColumnDefinition/>
            <ColumnDefinition Width="4"/>
        </Grid.ColumnDefinitions>
        <Rectangle Name="ResizeTopLeft" Fill="Black" Grid.Row="0" Grid.Column="0" MouseMove="ResizePressed" PreviewMouseDown="ResizePressed"/>
        <Rectangle Name="ResizeTop" Fill="Black" Grid.Row="0" Grid.Column="1" MouseMove="ResizePressed" PreviewMouseDown="ResizePressed"/>
        <Rectangle Name="ResizeTopRight" Fill="Black" Grid.Row="0" Grid.Column="2" MouseMove="ResizePressed" PreviewMouseDown="ResizePressed"/>
        <Rectangle Name="ResizeLeft" Fill="Black" Grid.Row="1" Grid.Column="0" MouseMove="ResizePressed" PreviewMouseDown="ResizePressed"/>
        <Rectangle Name="ResizeRight" Fill="Black" Grid.Row="1" Grid.Column="3" MouseMove="ResizePressed" PreviewMouseDown="ResizePressed"/>
        <Rectangle Name="ResizeBottomLeft" Fill="Black" Grid.Row="3" Grid.Column="0" MouseMove="ResizePressed" PreviewMouseDown="ResizePressed"/>
        <Rectangle Name="ResizeBottom" Fill="Black" Grid.Row="3" Grid.Column="1" MouseMove="ResizePressed" PreviewMouseDown="ResizePressed"/>
        <Rectangle Name="ResizeBottomRight" Fill="Black" Grid.Row="3" Grid.Column="2" MouseMove="ResizePressed" PreviewMouseDown="ResizePressed"/>
    </Grid>
</Window>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Runtime.InteropServices;
using System.Windows.Interop;

namespace WpfResizeWindow
{
    /// <summary>
    /// Window1.xaml      
    /// </summary>
    public partial class Window1 : Window
    {
        private const int WM_SYSCOMMAND = 0x112;
        private HwndSource _HwndSource;

        private Dictionary<ResizeDirection, Cursor> cursors = new Dictionary<ResizeDirection, Cursor> 
        {
            {ResizeDirection.Top, Cursors.SizeNS},
            {ResizeDirection.Bottom, Cursors.SizeNS},
            {ResizeDirection.Left, Cursors.SizeWE},
            {ResizeDirection.Right, Cursors.SizeWE},
            {ResizeDirection.TopLeft, Cursors.SizeNWSE},
            {ResizeDirection.BottomRight, Cursors.SizeNWSE},
            {ResizeDirection.TopRight, Cursors.SizeNESW},
            {ResizeDirection.BottomLeft, Cursors.SizeNESW} 
        };

        private enum ResizeDirection
        {
            Left = 1,
            Right = 2,
            Top = 3,
            TopLeft = 4,
            TopRight = 5,
            Bottom = 6,
            BottomLeft = 7,
            BottomRight = 8,
        }

        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        private static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);


        public Window1()
        {
            InitializeComponent();

            this.SourceInitialized += delegate(object sender, EventArgs e)
            {
                this._HwndSource = PresentationSource.FromVisual((Visual)sender) as HwndSource;
            };
            this.MouseLeftButtonDown += delegate(object sender, MouseButtonEventArgs e)
            {
                if (e.LeftButton == MouseButtonState.Pressed)
                    this.DragMove();
            };
            this.MouseMove += new MouseEventHandler(Window_MouseMove);
        }

        void Window_MouseMove(object sender, MouseEventArgs e)
        {
            if (Mouse.LeftButton != MouseButtonState.Pressed)
            {
                FrameworkElement element = e.OriginalSource as FrameworkElement;
                if (element != null && !element.Name.Contains("Resize"))
                    this.Cursor = Cursors.Arrow;
            }
        }

        private void ResizePressed(object sender, MouseEventArgs e)
        {
            FrameworkElement element = sender as FrameworkElement;
            ResizeDirection direction = (ResizeDirection)Enum.Parse(typeof(ResizeDirection), element.Name.Replace("Resize", ""));

            this.Cursor = cursors[direction];

            if (e.LeftButton == MouseButtonState.Pressed)
                ResizeWindow(direction);
        }

        private void ResizeWindow(ResizeDirection direction)
        {
            SendMessage(_HwndSource.Handle, WM_SYSCOMMAND, (IntPtr)(61440 + direction), IntPtr.Zero);
        }
    }
}