Where is System.Linq in .NET 4.0?

I migrated an asp.net app to 4.0. Now I am getting an error "The开发者_开发问答 type or namespace name 'IQueryable' could not be found". The reference to System.Linq is invalid and I can't find it in the reference list. Where did System.Linq go?

Make sure you are referencing System.Core.dll in your project. The IQueryable<T> type is defined in that assembly (just as it was in .NET 3.5).

Make sure you have a reference to System.Core.dll in your project - I believe System.Linq resides there.

It's in the System.Core.dll assembly.