Hello,

I did the steps from the tutorial you are using. I have received the same error when I did not do the last for steps specified:

12. Save all files

13. Unload the project and edit project‘s config file

 14. Add the following line under first <PropertyGroup> element

      <TokenReplacementFileExtensions>ashx</TokenReplacementFileExtensions>

15. Save file and reload project.

So be sure to do this:

1.Unload

sharepoint support ashx file