If you do ASP.NET development on a Windows 10 box and you’ve picked up the Fall Creators Update, you may have found that when you go to debug your code, you get an exception as soon as it tries to start: “System.InvalidOperationException: Failed to map the path ‘/App_GlobalResources/’.” After much digging around (and uninstalling and reinstalling Visual Studio 2017), I found the answer: go to the Control Panel, select “Programs and Features,” select “Turn Windows features on or off,” and make sure “Internet Information Services Hostable Web Core” is checked. Thank you, Microsoft, for unnecessarily breaking webapp development with a system update. Grr.

(The error described below happened when I tried switching my project from .NET Framework 3.5 to 4, thinking maybe that’d fix it. I switched it back to 3.5, as that’s what our webserver is running.)