每次单击收到的推送通知都会打开该应用程序的一个新示例。
我找到的文档和许多其他示例使用以下代码：

protected override void OnLaunched(LaunchActivatedEventArgs e)
    {
        Frame rootFrame = Window.Current.Content as Frame;

        // Do not repeat app initialization when the Window already has content,
        // just ensure that the window is active.
        if (rootFrame == null)
        {
            // Create a Frame to act as the navigation context and navigate to the first page.
            rootFrame = new Frame();

            rootFrame.NavigationFailed += OnNavigationFailed;

            if (e.PreviousExecutionState == ApplicationExecutionState.Terminated)
            {
                //TODO: Load state from previously suspended application.
            }

            // Place the frame in the current Window.
            Window.Current.Content = rootFrame;
        }

        if (rootFrame.Content == null)
        {
            // When the navigation stack isn't restored navigate to the first page,
            // configuring the new page by passing required information as a navigation
            // parameter.
            rootFrame.Navigate(typeof(MainPage), e.Arguments);
        }

        // Ensure the current window is active.
        Window.Current.Activate();
    }

但这对我不起作用。下面的代码行导致Window.Current.Content上出现NullReferenceException。

Frame rootFrame = Window.Current.Content as Frame;

我也注意到我的App类是从MauiWinUIApplication继承的，我想这就是重点，也许这个MauiWinUIApplication有不同的方法来处理这个问题，但是我找不到：

public partial class App : MauiWinUIApplication

如何防止每次单击推送通知时打开新示例？
我正在使用：Visual Studio社区2022 17.4.0，毛伊岛.Net 6
谢谢你！