When you have a project that explicitly targets the .NET Framework 4.6.2 or that disables the AppContext switch Switch.System.IO.UseLegacyPathHandling, Path.GetDirectoryName() and Path.GetPathRoot() throw an invalid path exception when they are passed a URI (such as http://).
This issue occurs because the same correctness check for colons that's used for the rest of the Path APIs was incorrectly added to these two APIs, which normally tolerate URI syntax.
To work around this issue, remove the URI prefix before you call these APIs. Or, set the AppContext switch Switch.System.IO.UseLegacyPathHandling=true.
The .NET Framework team is working to provide a fix for this issue in the future versions of the product.