Extending DocumentWindow

<docking:DocumentWindow x:Class="ActiproTest.Test"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:docking="http://schemas.actiprosoftware.com/winfx/xaml/docking"
    Height="300" Width="300">
    <Grid>         
    </Grid>
</docking:DocumentWindow>

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;

namespace ActiproTest
{
  /// <summary>
  /// Interaction logic for Test.xaml
  /// </summary>
  public partial class Test : ActiproSoftware.Windows.Controls.Docking.DocumentWindow
  {
    public Test()
    {
      InitializeComponent();
    }
  }
}