设计从外部控件获取其DataContext的WPF UserControl：如何在设计器中获取一些示例数据但在运行时使用继承的DC？

I am designing a WPF user control which contains other user controls (imagine a WidgetContainer, containing different Widgets) - using M-V-VM architecture. During development, I have WidgetContainerView in a window, window (View) spawns a WidgetContainerViewModel as its resource, and in a parameterless constructor of WidgetContainerViewModel, I fill its exposed collection with some sample widgets (WidgetViewModels).I am designing a WPF user control which contain