New Post: How do I translate this to Magick.net?

I have an image with a background and object in it, I have and image of just the background and I want to extract only the object.

This works for me:
convert overlay_figure.gif overlay_bgnd.gif -compose ChangeMask -composite overlay_removed.png

but I can't translate it properly to Magick.net, i always get a white/blank image

Can someone please translate the command properly for me?

Thanks in advance!