CS0246 and CS0433 errors when building .NET 4.0 website on Server 2012

Question

I am building a .Net 4.0 web project on Server 2012 with .Net 4.5 installed. I am using Psake under TeamCity and am getting CS0246 saying NotMapped could not be found, along with CS0433 saying it has found two DLLs for DataAnnotations.

The class looks like this:

using System.ComponentModel.DataAnnotations.Schema;
public abstract class Order
{
   [NotMapped]
   public decimal TaxPercentage { get; set; }
}

The full errors are:

Ordering\Order.cs(105,8): error CS0246: The type or namespace name 'NotMapped' could not be found (are you missing a using directive or an assembly reference?) [C:\TeamCity\buildAgent\work\71c853cb9b4c108\Code\Models\Model.csproj]
Ordering\Order.cs(105,8): error CS0433: The type 'System.ComponentModel.DataAnnotations.Schema.NotMappedAttribute' exists in both 'c:\TeamCity\buildAgent\work\71c853cb9b4c108\Code\packages\EntityFramework.5.0.0\lib\net40\EntityFramework.dll' and 'c:\Windows\Microsoft.NET\assembly\GAC_MSIL\System.ComponentModel.DataAnnotations\v4.0_4.0.0.0__31bf3856ad364e35\System.ComponentModel.DataAnnotations.dll' [C:\TeamCity\buildAgent\work\71c853cb9b4c108\Code\Models\Model.csproj]

The build works fine under Windows 8 using just Psake and not TeamCity. Any ideas how to resolve this?

Update: I've made a smaller test project and this builds fine on 2012. Looks like there's something weird with my main project.

Answer 1

Turns out System.ComponentModel.DataAnnotations shipped in EF 4.4, whereas they are in a separate assembly for EF 5.0. I had a mix of EF references in my projects which I have now rebuilt - all to use EF 5 and it's fixed the problem.