Error in a .g.cs file?

The .g.cs files in my projects are typically generated from XAML.

Check that the BreadcrumbLib isn't referenced in the xmlns references in any of your XAML files.

Try doing a clean. If that doesn't work, delete the bin obj directories in your solution, then do a full rebuild. Make sure none of your XAML files are referencing that component (which is what's generating the .g.cs file).