Navigate to web service implementation

I have a large ASP .Net solution I'm maintaining and it includes a number of web services and process/code that uses them. It would be useful to be able to navigate from a call to a web method to the actual method in the web service implementation. Currently all I can do is navigate to the Reference.cs implementation which is not much use. I've tried Referenced Code and Exposing Apis neither of which did what I need.

Am I missing something or is this just not possible?

VS 2017 + ReSharper Ultimate 2018.1