Question

When working with 5-tier architecture (front-end => interface tier => business tier => database tier => database) using WCF service as the interface tier, having the client applications calling it’s methods, should I use also WCF service for the business and database tiers? I ask because of all the serialization / deserialization that will be going on between the 3 services is probably going to consume a lot of CPU for the server, and have a performance impact on the application as a whole, or am I wrong?
In the case of running all 3 component layers on a single machine, is it better to build the business and database tiers as simple class libraries, and leave only the interface layer as WCF?
Tks

Answer 1

WCF is useful for communication between physical machines. Although you can use WCF to communicate intra-process there are simpler and more efficient ways to accomplish the same thing. You would only use WCF intra-process if you were thinking about putting the different layers on different machines at some point. As far as using WCF for the database tier, you wouldn’t: you would use the classes in the System.Data.xxx namespaces (ie System.Data.SqlClient if you are using a SQL server database; or possibly the Entity Framework).

Edits:

When people talk about 3-tier architecture they are mixing two concepts into one: physical tiers: a client machine, a middleware machine and a Database machine; and logical layers in the software architecture: client UI code, Business logic code, and data access code. When code from two different logical layers that reside on the same physical machine need to communicate the simplest model is one class calling into another, the amount of decoupling depends on your requirements. You want to use the simplest model that satisfies your requirements. Rockford Lhotka has an excellent description of this in the first chapter of his book Expert C# 2008 Business Objects