I am building a desktop application that will be used on local network, with SQL Server as database.
This application would have around 50 users top at the same time. In what particular scenario would I need to use WCF service? Is it recommended to create a WCF service on the server computer where database would reside, so we connect to this server through WCF service, instead of connecting to the database directly? What is the recommended way to connect to SQL Server data and why?
Edit: Let me explain in more detail. I have used WCF Ria services before, so I know how they work. Lets assume that WCF services works in same way. The question was directed toward why would we use WCF instead of directly connecting to database? I didnt want to specify my current application requirement, since I would get a specific answer for specific requirement. My goal was to understand in general why and when would you yse one instead of another. And I have received satisfying answers so far.
It appears to me that general consensus is to use WCF only if there would be a demand of another type of application, which would use web access to get data from service. Also, if I understood correctly, from security point of view, there is no difference between the two.
There would be a statistical app in the future that uses web to provide read-only statistics to user, and naturally some service will be required for this task (application has no specific client in mind, it will be offered to lots of clients). Since I need some demo application to be done very rapidly for particular clients, then I am thinking to neglect the service part, and make a proper layering (WPF->VM->Model->EF, so later I would just insert service between the model and EF. I guess it should not take too much time to make WPF app running with inserted layer. I am also postponing the service because of next reason: since HTML5 is (going to be) main technology for web, and there is a possibility that SL will be abandoned as technology (which I have been using), the logical decision would be to choose HTML5 over SL. But since I am totally unfamiliar with HTML5 and its requirements, I am not sure if WCF service is the best choice for it, and this is also one of the reasons to postpone the decision of choosing the service type (along with requirement to make the desktop demo app as fast as possible).
I think a better way to consider the question is whether you should abstract your database and data access layer from the application using a service interface. You could use WCF and SOAP or you could use a REST based HTTP service, the choice of technology is secondary to whether the current or future requirements of your application indicate that an additional layer of abstraction is warrented.
Reasons you might consider using a service interface instead of directly connecting to the SQL database include but are not limited to:
The trade off you are looking at is the time/cost/complexity of implementing a service interface versus the flexibility and mantainability benefits you will gain. You should evaluate the needs of your application and your customer before you make a decision on whether to connect directly to your data store using ADO.NET or use a service layer.
You should take a look at the Microsoft Service Layer Guidelines as they cover a lot of the considerations to take into account.