what the difference between the other way to update the UI thread from a background thread

[lindexi]

I want to know what the difference between

  await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
      CoreDispatcherPriority.Normal,()=>
      {
           //Up date
     });

and

   await Window.Current.Dispatcher.RunAsync(CoreDispatcherPriority.High,
           () =>
           {
               //Up date 
           });

[KarlErickson]

See CoreDispatcherPriority in the docs for info on this.

[oldnewthing]

Also, one dispatches to the main view, whereas the other dispatches to the current window.

[KarlErickson]

Thanks - I didn't see that part.

[lindexi]

Ths.If have no the current window as run in app.xaml.cs when the app running ,both will say null ref.And if it run in http await methor,the second will find the current is null.