Why is Visual Studio telling me I need to reference System.Private.CoreLib?
Do you have R# installed? You might have been hitting this issue: RSRP-464676
If so, try suspending R# and see if the issues are not shown anymore.
Do you have R# installed? You might have been hitting this issue: RSRP-464676
If so, try suspending R# and see if the issues are not shown anymore.