Visual studio hangs when inheriting from a web service reference client class

Question

I'm trying to work out why VS2015 hangs when I attempt to inherit from the auto-generated web service client class, which is itself a created as two partial classes.

To reproduce in Visual Studio 2015

1. Create a c# project
2. Add a web service reference to https://graphical.weather.gov/xml/SOAP_server/ndfdXMLserver.php?wsdl
3. Create a new class library file, make that class inherit from the webservice client class.

Begin to type a method body. Visual studio hangs.