C# Error “Is not supported by the language” after migration to .Net4

Question

I\'m trying to migration our website from .Net 3.5 to 4 and I\'m encountering a very weird issue.

Code that works just fine in 3.5 does not anymore once I target .Net4,

Answer 1

It's probably an assembly inconsistency issue. I had this problem when I wanted to use an assembly that created a circular reference with another project. Once I fixed this circular reference issue, the error didn't appear anymore.