Simple .NET Web.Config Transform Files

Let's say you have a web application, and you're ready to publish the changes either to test or production.  After you get the files published to the web server, you have to go into the web.config file and change the settings so that it points to the proper environment (database connection strings, web service URLs, etc.).  Most times you remember to do this, but sometimes you don't.  Or maybe you have somebody else do it, and they forget.  Or sometimes the web.config gets deleted from the web server, and you have to guess what all the settings were.  This is where a transformation file can really help.

Visual Studio automatically generates a transform file for both the release and debug configurations.  You can see these by clicking "Show All Files" and expanding the web.config.  The transform file is just a set of rules telling the publish profile how to change the web.config for that configuration.  A simple example is below:

  
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
  <system.serviceModel>
    <client>
      <endpoint name="TheWebServiceName" address="http://www.thisisfake.com/FictionalService.svc" xdt:Transform="SetAttributes" xdt:Locator="Match(name)" ></endpoint>
    </client>
  </system.serviceModel>
</configuration>

Our web application calls a web service that is at a different URL in production than in our development environment.  Above is a simple example of a transform file that changes the address attribute of the endpoint element when the name matches "TheWebServiceName".