creating Web Services to access from ASP and client desktop

I want to develop some data access web services in C# that can be accessed
from both an ASP.NET web application as well as a VC++ desktop application.
i have used web services in the past from VC++ by using the WSDL file
provided by the web service.

We are migrating our application to the web but still want to be able to
access the SQL Server database using the same data access layer.

What is the best way to create the web service so that it can be easily
accessed from VC++ desktop app and still be able to leverage all the web
support built in for web presentation layer data access?

Regards

Rob C