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 <DependendUpon> 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