Error in method Include LinQ: Unable to load type 'System.Data.Entity.DbExtensions'

I have an application of WindowsAplication in C # , it is developed in N-Layers . The method in the data layer to get a table did not give problems:

public List<styh_m_005_cultivo> GetAll()
{
    using (var context = new TermometroDbContext())
    {
        return (
            from entity in context.styh_m_005_cultivo
            select entity
        ).ToList();
    }
}

But when adding method include :

public List<styh_m_005_cultivo> GetAll()
{
    using (var context = new TermometroDbContext())
    {
        return (
            from entity in context.styh_m_005_cultivo
            select entity
        ).Include(c => c.styh_m_006_agricultor)
         .Include(c => c.styh_p_004_recinto).ToList();
    }
}

A System.TypeLoadException occurs:

  

Unable to load type System.Data.Entity.DbExtensions of assembly EntityFramework , Version=6.0.0.0 , Culture=neutral , PublicKeyToken=b77a5c561934e089 .