PowerPoint: How to get the current slide in multi-selected slides?

I selected multi-slides in the current presentation, But I want to get the slide which in the current document view.

I tried to use the following code for getting the slide,

Globals.ThisAddIn.Application.ActiveWindow.View.Slide

But it failed, I still got the first slide in the selected slides.

Any suggestion?

Create a event

Application.SlideSelectionChanged += Application_SlideSelectionChanged;
private void Application_SlideSelectionChanged(SlideRange SldRange)
{
    Debug.WriteLine(SldRange[1].SlideNumber);
}

gives u the current slideNumber in document view