The taskbar remains visiable when entering fullscreen mode in windows 7

I changed window style and topmost property for fullscreen senario,binding it to StateChanged event.

private void MainWindow_StateChanged(object sender, EventArgs e)
        {
            if (this.WindowState == WindowState.Maximized)
            {
                this.Visibility = Visibility.Collapsed;
                this.Topmost = true;
                this.WindowStyle = WindowStyle.None;
                this.ResizeMode = ResizeMode.NoResize;
                this.Visibility = Visibility.Visible;
            }
            else
            {
                this.Topmost = false;
                this.WindowStyle = WindowStyle.SingleBorderWindow;
                this.ResizeMode = ResizeMode.CanResize;
            }
        }

It works well in windows 10, windows 11 or windows 8.1 with WPF-UI library, while in windows 7(sp1) ,the taskbar cannot be hidden.I tried to remove WPF-UI and it behaves as expected.