A common question in TFS forums is how to populate list items from external sources in Work Items.
Well, there is not a specific functionality to integrate Work Items with external databases or systems when designing them. Actually, you will need to associate your Work Items fields with Global Lists and then have some automated process update this global list regularly.
Download this ImportGlobalList.zip file. I’ve put together a simple class (TfsGlobalList) that you can use to update global list items from a .NET application.
You could for example, create a simple Console App and schedule it using Windows Scheduler. This App would query a database and then update a TFS Global List using the provided code.
Note: the provided code must be run under an account with modify Global List permissions in TFS.
Note: remember to refresh Team Explorer in order to see updates in Work Item field values.