As you all should I am using web.config transformations during the packaging of my ASP.net web applications. Today I was working with a project which didn’t have transformations defined previously so I thought I would go ahead and add them. All went well until I built a deployment package and noticed that my transformations were not being applied. Looking at the build log I found warnings like these

C:UsersstimmsDocumentsVisual Studio 2010ProjectsSockPuppetWeb.Debug.config(5,2): Warning : No element in the source document matches '/configuration'
Not executing SetAttributes (transform line 18, 12)
Output File: objDebugTransformWebConfigtransformedWeb.config

This started a fun bit of debugging during which I removed everything from the web.config and built it from the ground up. Eventually I traced the problem to a hold over from some previous version of .net, in the Web.config the configuration was defined as

Changing that to just

Solved the problem. I imagine this is some sort of odd XML namespace issue, hopefully if you run into this you’ll find this post and not waste an hour like me.