How can I avoid RPC_E_WRONG_THREAD when updating my View Model?

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I'm working on a universal app to run on Windows 8.1 & Windows Phone 8.1. In the older Silverlight based Windows Phone apps, I could have a handy helper on my View Model something like:

protected delegate void OnUIThreadDelegate();
protected static void OnUIThread(OnUIThreadDelegate onUIThreadDelegate)
{
    if (onUIThreadDelegate != null)
    {
        if (Deployment.Current.Dispatcher.CheckAccess())
        {
            onUIThreadDelegate();
        }
        else
        {
            Deployment.Current.Dispatcher.BeginInvoke(onUIThreadDelegate);
        }
    }
}

From what I've seen of using async I should be able to do something like:

async void Watcher_PositionChanged(Geolocator sender, PositionChangedEventArgs args)
{
    this.Latitude = args.Position.Coordinate.Point.Position.Latitude;
    this.Longitude = args.Position.Coordinate.Point.Position.Longitude;

    // TODO: Consider reloading;
    var ev = await SpecialEvent.SearchNearAsync();
    this.Events.Clear(); // this is an ObservableCollection that the XAML is bound to,
                         // and I'm seeing it blow up with RPC_E_WRONG_THREAD here
}

Other options utilising the Dispatcher seem to be harder, as, in universal apps, Application.Current does not have a Dispatcher property?

So what are the options left? do I have to change my View-Models to allow the dispatcher to be passed from the View, or am I missing something more obvious?

asked 53 secs ago

Rowland Shaw

22.3k