Chapter 3. ER Diagrams, Domain Model, and N-Layer Architecture

In the last chapter, we saw the basic layering of the monolithic 1-tier 1-layer architectural style in action, with the UI layer having code-behind classes as the sub-layer. This 1-tier 1-layer architecture is the default style in ASP.NET and Visual Studio 2005/2008. To overcome the limitations of this style, we can further break the application code into n-layers, where the number "n" actually depends on the project requirements.

In this chapter we will:

Let's revisit the 1-tier ASP.NET application configuration described in the last chapter.

As mentioned in the last chapter, we can call this 1-tier architecture a 3-tier architecture if we include the browser and database (if used). For the rest of this chapter we will ignore the database and browser as separate tiers so that we can focus on how to divide the main ASP.NET application layers logically, using the n-layer pattern to its best use.

We will first try to separate the data access and logical code into their own separate layers and see how we can introduce flexibility and re-usability into our solution. We will understand this with a sample project. Before we go ahead into the technical details and code, we will first learn about two important terms: ER Diagram and Domain Model, and how they help us in getting a good understanding of the application we need to develop.