The type or namespace name 'Linq' does not exist in the namespace 'System'

Question

I have a wcf service hosted in a website in IIS and I seem to have this issue. In my web.config I have this:

Answer 1

The solution for me was to:

1. Go to: Tools > Nuget Package Manager > Manage NuGet Packages for Solution

2. Install the System.Linq package.