Unity Hololens System.web.httputils doesn't exist in target Framework

Question

I am trying to build an app for the Hololens. It already worked a lot of times, as I am developing since about 10 months. But all of a sudden, a reference is broken. I have appended a screenshot.

I have already tried (for weeks):

1. Downgrading to version before, I also tried all unity versions available since 2018
2. Reimporting all assets
3. Running a virus scanner because crypto mining malware can affect imports
4. Talked to Microsoft support
5. Did manual imports with a csc.rsp file
6. Tried building in unity and running in vs code.
7. Tried to delete the dlls
8. Tried to add missing dlls in a lot of places.
9. Creating a whole new project but error persists.
10. A lot of other things I can not remember right now.

It looks like Unity is not able to copy System.web.dll into the Temp\Staging folder. Kind regards

Answer 1

Since the build completes in the end, did you test deploying the app?

We have a similar list of errors when building our app, but it still works as expected when deployed to a HoloLens. It appears similar bugs have appeared a number of times before as well:

https://github.com/microsoft/MixedRealityToolkit-Unity/issues/3939 https://fogbugz.unity3d.com/default.asp?1146307_k5pfi2qqltmcvqm5