Linq-to-sql Compiled Query returns object NOT belonging to submitted DataContext?

Question

Compiled query:

   public static class Machines
   {
      public static readonly Func<OperationalDataContext, short, Machine>
          QueryMachineById = 
           CompiledQuery.Compile((OperationalDataContext db, short machineID) =>
           db.Machines.Where(m => m.MachineID == machineID).SingleOrDefault()
     );

     public static Machine GetMachineById(IUnitOfWork unitOfWork, short id)
     {
        Machine machine;

        // Old code (working)
        //var machineRepository = unitOfWork.GetRepository<Machine>();
        //machine = machineRepository.Find(m => m.MachineID == id).SingleOrDefault();

        // New code (making problems)
        machine = QueryMachineById(unitOfWork.DataContext, id);

        return machine;
     }

It looks like compiled query is returning result from another data context

  [TestMethod]
  public void GetMachinesTest()
  {
     using (var unitOfWork = IoC.Get<IUnitOfWork>())
     {
        // Compile Query
        var machine = Machines.GetMachineById(unitOfWork, 3);
        // In this unit of work everything works… 
        // Machine from repository (table) is equal to Machine from compile query.
     }

     using (var unitOfWork = IoC.Get<IUnitOfWork>())
     {
        var machineRepository = unitOfWork.GetRepository<Machine>();

        // Get From Repository
        var machineFromRepository = machineRepository.Find(m => m.MachineID == 2).SingleOrDefault();
        // Get From COmpiled Query
        var machine = Machines.GetMachineById(unitOfWork, 2);

        VerifyMachine(machineFromRepository, 2, "Machine 2", "222222", ...);
        VerifyMachine(machine, 2, "Machine 2", "222222", ...);

        Assert.AreSame(machineFromRepository, machine);       // FAIL
     }
  }

If I run other (complex) unit tests I'm getting as expected: An attempt has been made to Attach or Add an entity that is not new, perhaps having been loaded from another DataContext.

Another Important information is that this test is under TransactionScope (But problem is appearing even without transaction around.)!

I’m using POCOs mapped with DB using XML.

UPDATE: It looks like next link is describing similar problem (is this bug solved ?): http://social.msdn.microsoft.com/Forums/en-US/linqprojectgeneral/thread/9bcffc2d-794e-4c4a-9e3e-cdc89dad0e38

Answer 1

It is a bug and it will not be fixed.

Similar problem was described in the post from link below. I tried not to use PK in compiled query as suggested but got the same problem. So there is an issue with compiled queries bypassing the cache.

Workaround for LINQ to SQL Entity Identity Caching and Compiled Query Bug?

Answer 2

You can try setting the ObjectTrackingEnabled of the context to false. This helped me in this same situation but I later turn it on while updating and inserting records.

DBDataContext.ObjectTrackingEnabled = false; // Read Only