Have you ever wondered if/when a transaction in WCF upgrades to the DTC? There two simple ways to check this:

1. Open Performance Monitor and add a new counter. Get the counter Active Transactions from the Distributed Transaction Coordinator section.
2. Open Component Services and go to My Computer in COM+. There is a folder for Distributed Transaction Coordinator, through which you can view the DTC statistics.

In both cases, you'll see the active transactions jump from 0 to 1 when a transaction upgrades to DTC. This happens when you cross a service boundary. If you just use a transaction within the service, WCF will stick to the Lightweight Transaction Manager as long as you stay within you AppDomain or access a single database (SQL Server 2005 and up).