我使用WPF 4.0和MVVM光工具包，我有以下代码：

public partial class View1: Window
{
    /// <summary>
    /// Initializes a new instance of the FavoritesView class.
    /// </summary>
    public View1()
    {
        InitializeComponent();
    }

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {    
        Messenger.Default.Register<NotificationMessage>(this,
            (msg) =>
            {
                if (msg.Notification == "OpenDocument")
                {
                    DocumentView view = new DocumentView();
                    view.Owner=this;
                    view.ShowDialog();
                }
            });            
    }
}

当我多次打开-关闭DocumentView窗口时，我得到异常“无法将Owner属性设置为已关闭的窗口”。为什么？有什么想法吗？