I am writing a simple data- displaying app that has a UI presentation layer, a data access layer, and a commons layer which includes the data sets. Since this application will be relatively light weight (no writing / updating data) I figured it would be easier to use the Data Facade pattern instead of writing the Business Logic Layer.
The question: I have been following this article on Facades: http://msdn.microsoft.com/en-us/library/orm-9780596527730-01-04.aspx and in Fig 4.5 the Facade is written into the same library as the sub systems (which in my case would be the data adapters). Would you take this approach vs. writing a new C# class library for a Data Facade all together?
In my UI I am utilizing the Data Facade in this way:
public partial class MyDataApp : Form
{
DataFacade ApplicationDataFacade = new DataFacade();
}
According to the definition of the facade pattern, the point is to simplify complex libraries or APIs into simple ones using a class that creates a simple interface to the whole library.
So to answer your question, a facade pattern makes sense when complex libraries are involved, meaning it cant be a substitute to creating a business logic, it's an abstraction of it. If you choose to use a single class for the whole layer, it will have all those responsibilities in a single class, which is not what the facade pattern is after.
It's understandable to try to use this approach when the project is small, but remember to evaluate how much your system can grow in time, to avoid having hard times at maintenance.