ObjectContext disposed puzzle

Question

Hi,

I have the follwing method.

public List<MyEntity> GetMyEntities(MyObjectContext objCtx)
{
     using(MyObjectContext ctx = objCtx ?? new MyObjectContext())
     {
          retun ctx.MyEntities.ToList();
     }
}

The idea is, user of this method can pass in the objectcontext if they have. If not then a new objectcontext will be created.

If I am passing an object context to it, then it is getting disposed after the method is done. I was expecting only "ctx" variable gets disposed.

If I write a small app, to know the using and dispose mechanism. It is acting differently.

    class TestClass : IDisposable
{
    public int Number
    {
        get;
        set;
    }
    public string Str
    {
        get;
        set;
    }

    public ChildClass Child
    {
        get;
        set;
    }

    #region IDisposable Members

    public void Dispose()
    {
        Console.WriteLine("Disposed is called");
    }

    #endregion
}

class ChildClass : IDisposable
{
    public string StrChild
    {
        get;
        set;
    }



    #region IDisposable Members

    public void Dispose()
    {
        Console.WriteLine("Child Disposed is called");
    }

    #endregion
}
class Program
{
    static void Main(string[] args)
    {
        TestClass test = null;
        test = new TestClass();
        test.Child = new ChildClass();

        using (TestClass test1 = test ?? new TestClass())
        {
            test1.Number = 1;
            test1.Str = "hi";
            test1.Child.StrChild = "Child one";
            test1.Child.Dispose();
        }

        test.Str = "hi";
        test.Child.StrChild = "hi child";

        Console.ReadLine();
    }
}

In this example, "test1"gets disposed but not "test". Where as in the first case both ctx and objCtx get disposed.

Any ideas what is happening here with objectContext?

Thank you, Suresh