>I would like however to be able to benefit of the interface registration to instantiate the Web Service. If someone knows a way to achieve that with support to SoapClient30, I would be interested to know how?

I still didn't have the time to try that out, but I must raise the point again: .NET doesn't use the same SOAP client as we've been using in VFP. Rather, it has its own native classes for doing that, which should be better as they are managed code. Although we can use the SOAP toolkit in .NET by means of COM interop, this isn't good, as we're paying the price of COM overhead (when we really shouldn't need it).