I've done data driven testing with MSTest before. Prior to now, it's been solely with XML file data sources that have been defined inline in the [DataSource] attribute on my test.
I wanted to try using the app.config to define my data sources so that I could make them dynamic and configure them at test execution time so that I could point my tests at different environments.
I started following this tutorial on MSDN. It shows how to define data sources in the app.config for the tests. Then I followed the guidance in this post on the MSDN forums for how configure XML data sources in the app.config. Once I did that, I set up my XML data file similarly to the following:
<?xml version="1.0" encoding="utf-8" ?>
The second-level "dev" elements are the "data table" in the connection parameters for the data source. By naming these appropriately, I can now select the environment in which to run my tests as part of my automated builds (yay ALM).