Hi,
I have a windows application that has its business logic layer implemented as a WCF service. This service is currently hosted on IIS. I wanted to know that if there's a way where I could optionally run the application in standalone mode when a service isn't available/feasible.
In proper design, the business logic really shouldn't be implemented as a WCF service directly - it should abstracted out into a separate assembly for reasons just like yours, and the WCF wrapper should instead simply reference it. I'm guessing you didn't have a say in this non-orthogonal design.
If you have access to the WCF assemblies, you could distribute them with your standalone application and reference them, and then call into those WCF operations without activating it as a service. It would be rather ugly but it would work, assuming none of the business logic depends on any WCF-activated features.
edit re comments: You can have multiple service hosts and endpoints and keep the same contract ("interface") in WCF. Perhaps you want to add some self hosting that exposes a named pipe endpoint, and access the operations that way in your application.