Get exif from file without Image class

I am trying to get the jpg preview from a DNG file (not the thumbnail). From what I can tell, the preview is simply an exif preview, not specific to DNG. However as much googling as I do, I can't find anything about specifically getting the preview from the exif of a file in c#.

http://www.sno.phy.queensu.ca/~phil/...ames/EXIF.html

From this site it appears that the preview starts at Tag ID 0x0111, Group SubIFD1 for DNG. The length is at 0x0117, SubIFD1. But I don't really understand what the group means. I have used the Image.GetPropertyItem() before but I think that because the file is a DNG, it won't let me load it as an Image, I get an out of memory exception which apparently can mean that it's an unrecognized pixel format.

Is the image format integral to the exif information, or is there a way to read it without needing to decode the DNG?

I am aware that there are libraries made for opening DNG, but so far I have been unsuccessful in adapting these to my software and I would like to keep it fast and light. If I can just pluck this preview out it would really be a perfect situation.