DockSite serialization not working as expected

<Window 
    x:Class="ActiproSoftware.Windows.ProductSamples.DockingSamples.QuickStart.ProgrammaticCreation.MainWindow"
    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" 
    Title="Programmatic Creation QuickStart"
    Width="800" Height="600"
    >
    <DockPanel LastChildFill="True">
        <docking:DockSite x:Name="dockSite">
            <docking:SplitContainer>
                <docking:Workspace BorderBrush="#D0D0D0" BorderThickness="1">
                    <docking:Workspace.Background>
                        <LinearGradientBrush EndPoint="0,1">
                            <GradientStop Offset="0.5" Color="#FFFFFF" />
                            <GradientStop Offset="1" Color="#F8F8F8" />
                        </LinearGradientBrush>
                    </docking:Workspace.Background>
                    <StackPanel Margin="7">
                        <TextBlock Text="The Workspace" FontWeight="Bold" />
                        <Button Content="Serialize" Click="Serialize_Click" />
                        <Button Content="Deserialize" Click="Deserialize_Click" />
                        <ScrollViewer VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto">
                            <TextBlock x:Name="storage" />
                        </ScrollViewer>
                        <ScrollViewer VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto">
                            <TextBlock x:Name="events" />
                        </ScrollViewer>
                    </StackPanel>
                </docking:Workspace>
                <docking:ToolWindowContainer>
                    <docking:ToolWindow x:Name="originalToolWindow" Title="Original Tool Window" CanClose="False">
                        <TextBlock Text="Originally-created tool window" />
                    </docking:ToolWindow>
                    <docking:ToolWindow x:Name="anotherToolWindow" Title="Another Tool Window" CanClose="False">
                        <TextBlock Text="Another originally-created tool window" />
                    </docking:ToolWindow>
                </docking:ToolWindowContainer>
            </docking:SplitContainer>
        </docking:DockSite>
    </DockPanel>
</Window>

using System;
using System.Windows;
using ActiproSoftware.Windows.Controls.Docking;
using ActiproSoftware.Windows.Controls.Docking.Serialization;

namespace ActiproSoftware.Windows.ProductSamples.DockingSamples.QuickStart.ProgrammaticCreation
{
    public partial class MainWindow : System.Windows.Window
    {
        public MainWindow()
        {
            InitializeComponent();

            dockSite.WindowOpened += DockSiteEventHandler("WindowOpened");
            dockSite.WindowOpening += DockSiteEventHandler("WindowOpening");
            dockSite.WindowClosed += DockSiteEventHandler("WindowClosed");
            dockSite.WindowClosing += DockSiteEventHandler("WindowClosing");
        }

        private EventHandler<DockingWindowEventArgs> DockSiteEventHandler(string p)
        {
            return delegate(object sender, DockingWindowEventArgs e)
            {
                events.Text += p + Environment.NewLine;
            };
        }

        private void Serialize_Click(object sender, RoutedEventArgs e)
        {
            storage.Text = new DockSiteLayoutSerializer().SaveToString(dockSite);
        }

        private void Deserialize_Click(object sender, RoutedEventArgs e)
        {
            new DockSiteLayoutSerializer().LoadFromString(storage.Text, dockSite);
        }
    }
}