To fix this, one just has to update the .csproj file of the particular project by adding this line - make sure you point to the correct path of "Microsoft.Web.Publishing.Tasks.dll"
<UsingTask TaskName="TransformXml" AssemblyFile="$(MSBuildExtensionsPath)\Microsoft\VisualStudio\v16.0\Web\Microsoft.Web.Publishing.Tasks.dll" />
<Target Name="BeforeBuild">
<TransformXml Source="App.Base.config" Transform="App.$(Configuration).config" Destination="App.config" />
</Target>
<UsingTask TaskName="TransformXml" AssemblyFile="$(MSBuildExtensionsPath)\Microsoft\VisualStudio\v16.0\Web\Microsoft.Web.Publishing.Tasks.dll" />
<Target Name="BeforeBuild">
<TransformXml Source="App.Base.config" Transform="App.$(Configuration).config" Destination="App.config" />
</Target>
