I added an existing ASP.Net web application project to my solution. In addition to the standard debug and release configurations this solution also has two custom configurat
You must first define the configurations in the Configuration Manager. To be sure you are bringing up the Configuration Manager, you can access it by going to: Build->Configuraton Manager
In the Active Solution Configuration dropdown, select . Once you've added, you will then be able to "Add Config Transform".
Don't edit your solution file directly. It will only cause headaches.