Question

I am trying to implement an UnitOfWork type pattern where one DataContext is used over a short group of related methods and only at the end do I save the changes. However, I have found that entities added to the ObjectContext do seem to be available for reselection unless I SaveChanges, which is what I am trying to avoid. Can someone tell me if this is the expected behaviour? I have provided a psuedo test to illustrate:

    [Test]
    public void ObjectContext_ShouldSelectBackUncommitedValuesWhenUsingTheSameContext()
    {
        //arrange
        var entityConnectionString = "MyEntityConnectionString";
        var dataContext = new MyObjectContext(entityConnectionString);

        var personCount = dataContext.People.AsQueryable<Person>().Count();
        var person = new Person() { Name = "Bob" };

        //act
        dataContext.AddToPeople(person);

        //assert
        var actualPerson = dataContext.People.AsQueryable<Person>().Where(p => p.Name == "Bob").FirstOrDefault();
        Assert.IsTrue(actualPerson != null,"Uncommitted Person should return when using same context");

        var actualCount = dataContext.People.AsQueryable<Person>().Count();
        Assert.IsTrue(actualCount == personCount + 1, String.Format("Expected {0} people but got {1} people", personCount + 1, actualCount));

        //leave transaction to rollback

    }

This test fails with the actualPerson being null and the Count of the People set not incrementing. Forgive me if there are any typos as I have just simplified my own ObjectContext.

FYI I am using EF 4.

TIA.

–EDIT–
Further by way of analogy, I was hoping to be able to work with uncommitted objects as I can in SQL eg:

CREATE TABLE Person (Name nvarchar(10));
INSERT INTO Person VALUES ('Francois')
INSERT INTO Person VALUES ('Hans')

SELECT COUNT(*) FROM Person

BEGIN TRANSACTION
INSERT INTO Person VALUES ('Bob')
SELECT 'Bob Lives!' WHERE EXISTS(SELECT * FROM Person WHERE NAME='Bob')
ROLLBACK TRANSACTION

DROP TABLE Person

Answer 1

Doing this

dataContext.People.AsQueryable<Person>().Where(p => p.Name == "Bob").FirstOrDefault();

actually results in a database call, so it shouldn’t return any unpersisted data.
If you want to get your person back, you have to use ObjectStateManager:

dataContext.ObjectStateManager.
           GetObjectStateEntries(EntityState.Added | EntityState.Deleted | 
                                 EntityState.Modified | EntityState.Unchanged).
           Where(ent => ent.Entity is Person).
           Select(ent => ent.Entity as Person).
           Where(p => p.Name == "Bob").
           FirstOrDefault();