单独桌面中的WPF窗口在Win10中运行，而不是在Win7中运行

Question

我正在尝试在单独的桌面上打开WPF窗口。在Windows 10中，下面的代码按预期工作并显示此窗口：

但是，在Windows 7中，文本未显示，Windows壁纸渗透：

我认为代码很简单：

using System;
using System.Threading;
using System.Windows;
using System.Windows.Controls;
using System.Runtime.InteropServices;

class Program
{
    const uint GENERIC_ALL = 0x10000000;

    [DllImport("kernel32.dll")] static extern uint GetCurrentThreadId();
    [DllImport("user32.dll")]   static extern IntPtr GetThreadDesktop(uint dwThreadId);
    [DllImport("user32.dll")]   static extern IntPtr CreateDesktop(string desktopName, IntPtr device, IntPtr deviceMode, uint flags, uint accessMask, IntPtr attributes);
    [DllImport("user32.dll")]   static extern bool SetThreadDesktop(IntPtr hDesktop);
    [DllImport("user32.dll")]   static extern bool CloseDesktop(IntPtr hDesktop);
    [DllImport("user32.dll")]   static extern bool SwitchDesktop(IntPtr hDesktop);

    [STAThread]
    public static void Main()
    {
        var btn = new Button() { Content = "Open secure desktop" };
        btn.Click += (s, e) => SecureDialog();
        var win = new Window() { Content = btn };
        new Application().Run(win);
    }

    static void SecureDialog()
    {
        var hOldDesktop = GetThreadDesktop(GetCurrentThreadId());
        var hNewDesktop = CreateDesktop("My desktop", IntPtr.Zero, IntPtr.Zero, 0, GENERIC_ALL, IntPtr.Zero);
        SwitchDesktop(hNewDesktop);

        var thread = new Thread( () => SecureDesktopThread(hNewDesktop) );
        thread.SetApartmentState(ApartmentState.STA);
        thread.Start();
        thread.Join();

        SwitchDesktop(hOldDesktop);
        CloseDesktop(hNewDesktop);
    }

    static void SecureDesktopThread(IntPtr hNewDesktop)
    {
        SetThreadDesktop(hNewDesktop);
        var win = new Window() { Content = "Hello World!", FontSize=30 };
        win.ShowDialog();
        System.Windows.Threading.Dispatcher.CurrentDispatcher.InvokeShutdown();
    }
}

那么，为什么Win7上的行为不同？我在这里错过了什么吗？