EF: How do I call SaveChanges twice inside a transaction?

Using Entity Framework (code first in my case), I have an operation that requires me to call SaveChanges to update one object in the DB, and then SaveChanges again to update another object. (I need the first SaveChanges to resolve an issue where EF can't figure out which object to update first).

I tried doing:

using (var transaction = new TransactionScope())
{
    // Do something

    db.SaveChanges();

    // Do something else

    db.SaveChanges();

    tramsaction.Complete();
}

When I run that, I get an exception at the second SaveChanges call, saying "the underlying provider failed on open". The inner exception says that MSDTC is not enabled on my machine.

Now, I've seen posts elsewhere that describe how to enable MSDTC, but it seems that I would also need to enable network access, etc. This sounds like complete overkill here, since there are no other databases involved, let alone other servers. I don't want to do something that's going to make my whole application less secure (or slower).

Surely there must be a more lightweight way of doing this (ideally without MSDTC)?!

It is probably caused by two different connections used in your transaction. Try to control connection for your operation manually:

var objectContext = ((IObjectContextAdapter)db).ObjectContext;

try {
    //Open Connection
    objectContext.Connection.Open();

    using (var transaction = new TransactionScope()) {
        // Do something

        db.SaveChanges();

        // Do something else

        db.SaveChanges();

        transaction.Complete();
    }
} finally {
    //Close connection after commit
    objectContext.Connection.Close();
}