Integrating applications with projects in Visual Studio 2008?

We need to integrate our application with a client's applications, and this integration will happen through开发者_开发百科 WebServices.

We will have to instantiate different classes depending on which release the client is on. The thing is, I don't know how other companies do that, we were thinking about some dynamic assembly loading for code readability or manage this through pre-processor directives.

What do you suggest?

I might not understand very well your question (maybe you could add some more details) but doesn't the Factory pattern suit your needs?

EDIT: This may help too: http://martinfowler.com/articles/enterprisePatterns.html