I have two classes that are creating UnitOfWork2 objects. I would like to combine those into a single UnitOfWork2 (or at least execute the queries in a single transaction).

What is the best way to accomplish this?

There is no an explicit method to merge to UnitOfWork objects. You can do it manually though: retrieving the elemensTo/Insert/Delete/Update and then adding them to the second uow.

As you want to save them in one transaction, you can start a transaction outside and pass it to the commit method of the uow's. As the transaction is already started, uow will use that and won't start a new one. Example:

using (var adapter = new DataAccessAdapter())
{
    adapter.StartTransaction(IsolationLevel.Serializable, "TwoUowInARowTx");

    uow1.Commit(adapter);
    uow2.Commit(adapter);

    adapter.Commit();
}

Thanks, daelmo. The code example gave me the right idea for what I should be doing in this application. That is better than a merge.