BitmapSource from file

• The BitmapImage class is a non-abstract subclass of BitmapSource, so just use the BitmapImage(Uri) constructor and pass that new instance to anything that expects a BitmapSource object.
• Don't be confused by the fact the argument type is System.Uri: a Uri isn't just for http:// addresses, but it's also suitable for local filesystem paths and UNC shares, and more.

So this works for me:

BitmapImage thisIsABitmapImage = new BitmapImage(new Uri("c:\\image.bmp"));

BitmapSource thisIsABitmapImageUpcastToBitmapSource = thisIsABitmapImage;