Three Layer Architecture in C# .NET

First let me give you a small overview about the topic I would like to cover in this article.

1. Tier vs. Layer
2. Three Tier/Layer Architecture Design Components
3. Demo: Three Layer Windows Application in C#.NET

4. 1. Tier vs. Layer

   1.1 Tier: Tier indicates a physical separation of components, which may mean different assemblies such as DLL, EXE, etc. on the same server or multiple servers.
   As you can see in the above figure, Data Tier have no direction with Presentation Tier, but there is an intermediate Tier called Business Tier which is mainly responsible to pass the data from Data Tier to Presentation Tier and to add defined business logic to Data.
   So, if we separate each Tier by its functionality, then we come to know the below conclusion:
   
   1.2 Layer: Layer indicates logical separation of components, such as having distinct namespaces and classes for the Database Access Layer, Business Logic Layer and User Interface Layer.
   

   2. Three Tier/Layer Architecture Design Components

   As we have already seen, tier is the sum of all the physical components. We can separate the three tiers as Data Tier, Business Tier and Presentation Tier.
   
5. Data Tier is basically the server which stores all the application’s data. Data tier contents Database Tables, XML Files and other means of storing Application Data.
6. Business Tier is mainly working as the bridge between Data Tier and Presentation Tier. All the Data passes through the Business Tier before passing to the presentation Tier. Business Tier is the sum of Business Logic Layer, Data Access Layer and Value Object and other components used to add business logic.
7. Presentation Tier is the tier in which the users interact with an application. Presentation Tier contents Shared UI code, Code Behind and Designers used to represent information to user.

The above figure is a mixture of Three Tier and Three Layer Architecture. Here, we can clearly see a different between Tier and Layer. Since each component is independent of each other, they are easily maintainable without changing the whole code.
This approach is really very important when several developers are working on the same project and some module needs to be re-used in another project. In a way, we can distribute work among developers and also maintain it in the future without much problems.
Testing is also a very important issue for Architecture when we are considering writing a test case for the project. Since it’s like a modular architecture, it’s very handy testing each module and to trace out bugs without going through the entire code.

3. Demo: 3 Layer Windows Application in C#.NET

Let’s go though from one module to other to have a better understanding of it.

Part1

Part 2

Part 3

Part 4

                                                                                                                                                                                                                    Theory By Codeproject.com