WPF用户控制窗口启动位置

如何得到UserControl中Window的WindowStartupLocation性质?

public partial class ActivityDetailsView : UserControl
{
    public ActivityDetailsView(ActivityDetailsViewModel viewModel)
    {
        InitializeComponent();
        DataContext = viewModel;
        Loaded += ActivityDetailsView_Loaded;
        JobOrderLineItem.SelectionChanged += JobOrder_SelectionChanged;
        //this.WindowStartupLocation doesnt exist
    }
}

public partial class ActivityDetailsView : Window
{
    // ...
}