I installed the SlowCheetah package via nuget and added transform files for my web.config based on Build config. However, on building, the web.config does not get transform
Visual Studio is doing Transformation only when you deploy your project by using the publish functionality. To do it when you do the build you need to tweak your MSBuild script. The complete solution is here. Here the essentials:
Files in project Create a file named Web.Base.config, besides the existing Web.Debug.config and Web.Release.config. This file will be the equivalent to your old Web.config, as it will be the base for the tranformation. You will end up with these files:
Web.config, Web.Base.config, Web.Debug.config, Web.Release.config, and Web.config. Add the following configuration to the bottom of your .csproj-file, just before the closing -tag:
UPDATE: From a reminder in the comments I realized that I also have a problem with Visual Studio transforming the XML twice, when Publishing a project. The solution to this is to add a Condition to the Target-tag like this: