Can't add System.Data.Linq or System.Web to project

Question

I can't add System.Data.Linq or System.Web to project, each time I do I get a warning symbol yellow !, on the reference

Any ideas why?

I had it working all okay this morning

Answer 1

Sounds like the path to the DLL may no longer be valid. Try removing the reference and adding it in again...

Answer 2

Did you change the .Net version of the project.

System.Data.Linq does not work for .Net 2.0.

Answer 3

I've had to create a new project and copy the classes and now it is working.