Why check Dictionary for non UN VR after reading the length?

[Aerik Sylvan]

In DicomReader.ParseDataset, there is a section with the comment, 

"check dictionary for VR after reading length to handle 16-bit lengths"

but this happens in the ParseState.Value block, after the _length has already been set.  What is the rationale for that?  I do not see the length being reset.

I'm asking because I have some files with sequences marked as UN VRs, and they break because the length is read incorrectly.  I'm going to try putting that check earlier in the code, *before* the length is read.

Any input?

Thanks,

Aerik