How do I add PI Web API as web service to a .Net project?

How do I add PI Web API as web service to a .Net project?

I can access the PIWebAPI through the browser but when I try to add it to my .Net web application project in Visual Studio as a Web Service Reference I get the following error:

An error occurred while attempting to find services at 'https://xxxxxxxx/PIwebapi'. The data at the root 

Metadata contains a reference that cannot be resolved: 'https://xxxxxxx/PIwebapi'.