Image.Source = new BitmapImage(); doesn't work in UWP

Question

I have a problem while reading a file in C#. Here's the code:

protected override void OnNavigatedTo(NavigationEventArgs EvArgs)
    {
        base.OnNavigatedTo(EvArgs);
        var Args = EvArgs.Parameter as Windows.ApplicationModel.Activation.IActivatedEventArgs;
        var FArgs = Args as Windows.ApplicationModel.Activation.FileActivatedEventArgs;
        if (Args != null)
        {
            if (Args.Kind == Windows.ApplicationModel.Activation.ActivationKind.File)
            {
                var IMG = new Image();
                IMG.Loaded += IMG_Loaded;
                string FP = FArgs.Files[0].Path;
                Uri = FP;
                IMG.Source = new BitmapImage(new Uri(FP, UriKind.RelativeOrAbsolute));
                FV.Items.Add(IMG);
                PathBlock.Text = FArgs.Files[0].Name + " - Image Viewer";

                void IMG_Loaded(object sender, RoutedEventArgs e)
                {
                    IMG.Source = new BitmapImage(new Uri(Uri));
                }
            }
        }
        if (Args == null)
        {
            PathBlock.Text = "Image Viewer";
        }
    }

The problem is at this part:

IMG.Source = new BitmapImage(new Uri(FP, UriKind.RelativeOrAbsolute));

The image won't load, even after trying a resource that the app CAN access in its own files:

IMG.Source = new BitmapImage(new Uri("ms-appx:///09.png, UriKind.RelativeOrAbsolute));

It still won't work. This only works with this code:

var FOP = new Windows.Storage.Pickers.FileOpenPicker();
StorageFile F = await FOP.PickSingleFileAsync();
IRandomAccessStream FS = await F.OpenAsync(FileAccessMode.Read);
var BI = new BitmapImage();
var IMG = new Image();
await BI.SetSourceAsync(FS);
IMG.Source = BI;

Sadly, I can't use a file stream OR a file picker in the first code example, so I can't make it work as I did here.