找到解决方案elsewhere on StackOverflow：我为NavigationService创建了一个 Package 器：

public static class Navigator
{
    private static NavigationService NavigationService {get;} = (Application.Current.MainWindow as MainWindow).mainFrame.NavigationService;

    public static void Navigate(string path, object param = null)
    {
        NavigationService.Navigate(new Uri(path, UriKind.RelativeOrAbsolute), param);
    }

    public static void GoBack()
    {
        NavigationService.GoBack();
    }

    public static void GoForward()
    {
        NavigationService.GoForward();
    }
}

首先设置一个帧（在xamel主窗口中渲染）

<DockPanel>
    <Frame x:Name="mainFrm" />
</DockPanel>

然后使用navigate，因此出现空引用异常

mainFrm.NavigationService.Navigate(new Uri("ShopPage.xaml", Game.CurrentShop));

如果您在控制器操作代码块中，请使用下面的代码

void ExampleControllButton_Click(object sender, RoutedEventArgs e)
{
this.NavigationService.Navigate(new Uri("ShopPage.xaml", Game.CurrentShop));
}

如果框架元素在主窗口中，则将其添加到MainWindow.xaml.cs：

public static NavigationService NavigationService => ((MainWindow)Application.Current.MainWindow).frmMain.NavigationService;

注意：frmMain是XAML文件中框架的名称

<Frame x:Name="frmMain" />

使用方法：

MainWindow.NavigationService.Navigate("ShopPage.xaml", Game.CurrentShop);