I started a project from the DirectX and XAML template and made some small edits to the Direct3D-only portion of the project.
Now I get a number of errors in the xamltypeinfo.g.cpp file, stating that the Common::NavigationHelper class doesn't exist. Hovever I can validate that it's definitely a class included in the template, but it looks like whatever generated these files didn't include it.
I don't want to go messing around with generated files, and I haven't touched any of the XAML code at all in the template.
I created another project walking through the steps I had performed, and ran a diff on the two projects. The entire Common directory (and namespace, which included NavigationHelper) was unique to the original project.
I then remembered that at one point I had accidentally added a XAML page. I promptly removed it, which seems to have left these files included but they weren't included by another other file. Visual Studio still generated references to them, thus the errors.
It looks like if you add any XAML pages that require navigation, pulling them out is not as simple as removing the file. You must also remove the navigation infrastructure as well, by removing all references to the Common folder that were added to your project.