Web.Config Transformation not working
From Logic Wiki
The Web.config transforms are only applied as part of a publish operation.
If it has to be done as part of the build operation, then SlowCheetah - XML Transforms Visual Studio plugin must be installed.
https://visualstudiogallery.msdn.microsoft.com/69023d00-a4f9-4a34-a6cd-7e854ba318b5
