New Post: ToByteArray returns all zeros

I have the following code for a WinRT project:

Async Function SetImage(imagestream As IRandomAccessStream, image As Image) As Task
    
    Dim Bitmap As New BitmapImage
    Dim Bytes As Byte()
    
    ' Note
    Bitmap.SetSource(imagestream) ' I get the width and height of the image from this
    Dim Wbm as WriteableBitmap = New WriteableBitmap(Bitmap.PixelWidth, Bitmap.PixelHeight)
    image.Source = Await Wbm.FromStream(imagestream)
    Bytes = Wbm.ToByteArray

End Function

The image appears correctly on-screen after this function
However, The Bytes array contains all zeros. I need the byte array to store the image in my program's database. It obviously isn't working.

Is there something I'm not understanding about 'ToByteArray'?