I recently wrote a wrapper (C#) for an ApplinX web service - this is a product that is part of the Software AG Adabas offering. The web service interface is really primitive and I wrote the wrapper to make it easier to use.
The wrapper is in use on web applications (C# + Asp.Net) but I want to a Windows client to access it using WCF. Would it be better to write the WCF services from scratch or simply wrap the existing wrapper in WCF?
Is the wrapper in a seperate class library? If not, you can move the wrapper into a class ibrary and allow both the ASP.NET app and the windows client app to consume it. This would eliminate any adition wrappers and abstraction layers. It would also allow the windows client to directly consume the service without having to go through the ASP.NET application.
If you wrap the current wrapper in as a WCF service, then from the windows client, you will be making a service call to your ASP.NET app, which will turn around and make another call to the service it is consuming. The above recommendation will eliviate that. If however there is some business logic you need to encapsulate and only want to be on the server, then I would create a WCF service on the ASP.NET application and wrap the calls to your wrapper service in that. The Windows client can then consume the WCF service.