Visual Studio Does not recognize System.Linq

Question

I created this program and C# and it worked correctly a few weeks ago. Now, I copied all of this code to a another project I am working on. I added it to a brand new C# Cla

Answer 1

For me I tried this and worked:

PROJECT==>Add Reference ==> Browse ==> C:\Windows\winsxs\x86_netfx35linq-system.core_31bf3856ad364e35_6.1.7601.17514_none_6161fc35ed136622\System.core.dll

Or

you can simply find the System.core.dll using windows search on Os System Drive