WPF Form in Windows Forms Multi Document Interface

using System;
using System.Windows.Forms;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Interop;
using System.Runtime.InteropServices;

namespace WinformsMDIwithWPFChild {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
        }

        [DllImport("user32.dll")]  
        public static extern IntPtr SetParent(IntPtr hWndChild, IntPtr hWndNewParent);

        private void Form1_Load(object sender, EventArgs e) {
            //Add WPF Window
            WPFWindow w = new WPFWindow();
            System.Windows.Forms.Integration.ElementHost.EnableModelessKeyboardInterop(w);
            WindowInteropHelper helper = new WindowInteropHelper(w);
            helper.Owner = this.Handle;
            w.Show();
            SetParent(helper.Handle, this.Handle);
        }
    }
    // class creates WPF Window
    public class WPFWindow : Window {
        private Canvas canvas = new Canvas();
        private TextBlock block = new TextBlock();
        public WPFWindow() {
            this.WindowStyle = WindowStyle.ToolWindow;
            this.Background = System.Windows.Media.Brushes.White;

            this.Width = 250;
            this.Height = 250;
            canvas.Width = this.Width;
            canvas.Height = this.Height;
            canvas.Background = System.Windows.Media.Brushes.White;
            block.Text = "WPF";  
            block.FontSize = 20;
            canvas.Children.Add(block);
            this.Content = canvas;
        }
    }
}