I was preparing a demo about IIS XML Transformation inside a CD pipeline with Azure DevOps.

It’s very likely that if you’re working with an ASP.Net project with default values the Azure App Service Deploy Task will fail. After some googling I found that this is documented here.

The trick is to remove the tag inside the csproj file.

By default, MSBuild applies the transformation as it generates the web package if the <DependentUpon> element is already present in the transform file in the *.csproj file. In such cases, the Azure App Service Deploy task will fail because there is no further transformation applied on the Web.config file. Therefore, it is recommended that the <DependentUpon> element is removed from all the transform files to disable any build-time configuration when using XML transformation.

File transforms and variable substitution reference, XML transformation notes, Microsoft Docs