Consuming a web service using WSDL in class library

Hi,
I have been given a URL to a WSDL file so that I can access a web service.  I tried adding it to a web project by selecting Add Service Reference, then Advanced, then Add Web Reference.  It worked fine.  I created an instance of the proxy class that was generated and could call the methods.
All good so far.
I then tried adding it to a class library using the same approach, but it seems to have created .datasource files instead, and when I try to create an instance of the proxy class, it isn't recognised by Visual Studio (VS 2010 Pro).

Is it at all possible to add a web reference based on a WSDL file to a class library?

EDIT:  Problem solved.  In order to reference the service, I had to fully qualify it with the namespace it was nested within.  My class was in the namespace Processing, so I had to use using Processing.ServiceRequest;